The Secretary of Health and Human Services, concluding that Harry Gallant was not disabled within the meaning of the Social Security Act, denied his claim for Social Security disability benefits. 42 U.S.C. § 423. The district court affirmed the Secretary’s decision. Gallant appeals to this court and we reverse.
FACTS
Harry Gallant was born in 1934, and has completed nine years of formal schooling. He worked for 25 years as an operating engineer, operating heavy equipment and as a truck driver hauling heavy equipment. Claimant sustained his injury on October 25, 1978, as a result of falling four to five feet from a piece of machinery while at work. Subsequently, a myelogram was performed and in November, 1978, he underwent surgery for a herniated disc and was off work for approximately five months. Claimant attempted to continue his former employment, but after three and a half weeks he was forced to terminate because of his back problems.
Thereafter, claimant was treated by Drs. Bloemendaal and Syrenne and was evaluated at the pain clinic at Harborview Medical Center, Seattle, Washington in September and October, 1980. Tests revealed claim*1452ant had a posterior disc protrusion and on October 23, 1980, he underwent surgery for laminectomy, foraminectomy and fusion.
Claimant thereafter moved to Arizona and was treated by Drs. Lewis and Shetter and was hospitalized at the pain clinic at St. Joseph’s Hospital from February 6, 1982 to March 5, 1982, where he was seen by Drs. Thomas, Ginsberg and Collier. Until the hearing before the administrative law judge (ALJ) Gallant continued under the treatment of Dr. Ginsburg, Dr. Shetter and Dr. Thomas. Claimant has not worked since January 1980.
Claimant filed for disability insurance benefits on June 11, 1981, claiming disability commencing October 25, 1978. His application was denied both initially and on reconsideration. Gallant requested a hearing and on June 4, 1982 he appeared before the AU with his counsel.
Based on the evidence submitted at the hearing, the ALJ found claimant suffers from the following medically determinable impairments: status post back surgery, November 1978 and October 1980; chronic low back pain syndrome; and mild depressive neurosis. However, the ALJ found that claimant's impairments, while at a level of severity to prevent him from engaging in his past medium to heavy work, were not of such a level to prevent him from engaging in light and sedentary forms of substantial gainful activity. Therefore, the ALJ denied claimant’s disability claim.
Gallant brought an action in the district court for judicial review of this decision pursuant to 42 U.S.C. § 405(g). On cross motions for summary judgment, the district court denied Gallant’s motion for summary judgment and granted that of the Secretary. This appeal followed.
STANDARD OF REVIEW
On judicial review, the Secretary’s determination that a claimant is not disabled will be upheld if the findings of fact are supported by substantial evidence, 42 U.S.C. § 405(g), and the Secretary applied the proper legal standards. Hall v. Secretary of HEW, 602 F.2d 1372, 1374-75 (9th Cir.1979). Substantial evidence means more than a mere scintilla of evidence. “ ‘It means such relevant evidence as a reasonable mind might accept as adequate to support a conclusion.’ ” (Richardson v. Perales, 402 U.S. 389, 401, 91 S.Ct. 1420, 1427, 28 L.Ed.2d 842 (1971) (quoting Consolidated Edison Co. v. NLRB, 305 U.S. 197, 229, 59 S.Ct. 206, 216, 83 L.Ed. 126 (1938)).
DISCUSSION
In order to qualify for Social Security disability benefits a claimant must establish that a medically determinable physical or mental impairment prevents him from engaging in substantial gainful activity. 42 U.S.C. § 423(d)(1)(A). The impairment must result from abnormalities which are demonstrable by medically acceptable clinical or laboratory diagnostic techniques, 42 U.S.C. § 423(d)(3), and must be expected to result in death or last for a continuous period of at least 12 months. 42 U.S.C. § 423(d)(1)(A).
The claimant has the burden of proving disability within the meaning of the Social Security Act. Maounis v. Heckler, 738 F.2d 1032, 1034 (9th Cir.1984). “However, after a claimant establishes a prima facie case of disability by showing his inability to perform former work, the burden shifts to the Secretary to prove that the claimant can engage in other types of substantial gainful work that exists in the national economy.” Id.
Conceding the evidence supported Gallant’s claim that he was unable to perform his former work, the ALJ found, however, that Gallant could engage in light and sedentary forms of substantial gainful employment.
a. Substantial Evidence
Gallant contends that substantial evidence is lacking to support the AU’s conclusion that claimant is not subject to any significant impairment that significantly limits his ability to engage in light and sedentary forms of gainful activity.
*1453The inquiry here is whether the record, read as a whole, yields such evidence as would allow a reasonable mind to accept the conclusions reached by the AU. Richardson v. Perales, 402 U.S. at 401, 91 S.Ct. at 1427; Sample v. Schweiker, 694 F.2d 639, 642 (9th Cir.1982). Where evidence is susceptible of more than one rational interpretation, it is the AU’s conclusion which must be upheld, Rhinehart v. Finch, 438 F.2d 920, 921 (9th Cir.1971); and in reaching his findings, the AU is entitled to draw inferences logically flowing from the evidence. Beane v. Richardson, 457 F.2d 758 (9th Cir.), cert. denied, 409 U.S. 859, 93 S.Ct. 144, 34 L.Ed.2d 105 (1972).
At the hearing before the AU, claimant testified that his major complaints were of constant low back pain and aching in both legs. Claimant testified that he rises daily at approximately 7:30 a.m., retires around midnight, and is in severe pain throughout the day. While the AU noted claimant performs household chores including his own cooking, the record reveals claimant testified he did no housework, but cooks a meal for himself and his nephew or sister-in-law and does the dishes.
Claimant testified he could not sit over 10 minutes or stand over half an hour without back pain. He estimated he could lift between 5 to 10 pounds. He takes several walks a day for about 20 to 25 minutes each, walking about a block or block and a half, resting and then returning home and swims about 8 to 10 times a day averaging 5 minutes at a time.
The medical evidence submitted at the hearing reveals that claimant underwent surgery for a herniated disc in 1978 and a laminectomy and foraminectomy in 1980; and that, although claimant has recovered well in terms of reduced motor capabilities, he remains in constant low back pain and has been limited both in flexion and extension. This constant pain has prompted physicians to recommend that claimant wear a lower back brace as well as a lumbar flexion jacket. Medical reports indicate pseudoarthrosis is present, requiring claimant to undergo an exploration and repair of the lumbosacral pseudoarthrosis.
Thus the record indicates, and the Secretary acknowledges, that the claimant has shown that his impairments prevent him from continuing in his former employment. The fact of the claimant’s physical impairments, at least as they relate to his back condition, are not in dispute. It is rather the. severity of the impairments and the extent to which they limit his ability to engage in other employment that are in question.
After reviewing the numerous medical records indicating claimant’s significant continuing physical impairments and consistent complaints of chronic pain, the AU found the claimant’s medically determinable impairments do not meet or equal the severity of the “Listing of Impairments” for presumed disability found in Appendix 1 to Subpart P of the Code of Federal Regulations. 20 C.F.R. pt. 404, subpart P, app. 1. The AU then concluded that the functional limitations imposed by claimant’s exertional impairments restricted his ability to engage in sustained activity on a regular basis and deprived claimant of his ability to engage in medium and heavy work, but that claimant retained the ability to engage in light and sedentary work on a regular basis.
Although the AU did not indicate precisely what medical evidence required this decision, he referred to the reports of two doctors. Dr. Frankel estimated claimant would be prevented from engaging in his past work for four to six months after his second back surgery; and Dr. Shetter stated that, as of April 2, 1982, “there was no evidence of nerve root compromise or sten-osis,” and specified that “further surgery was not indicated.” The latter report, however, also noted that the evaluation of claimant at St. Joseph’s Hospital pain clinic suggested the possibility of a pseudoar-throsis and referred claimant to a Dr. Ginsberg for evaluation. Although the AU referred to the report of Dr. Ginsberg dated May 12, 1982, confirming the presence of pseudoarthrosis and indicating the possi*1454bility of future surgery, the AU found that “even with the possibility of future surgery, there are no objective findings of record which support a conclusion that claimant is precluded from engaging in light exertional activity.” The AU concluded that “while no doubt claimant does have residual chronic pain and discomfort,” such is not severe, but mild to moderate, and does not prevent claimant from performing light work.1
Contrary to the AU’s conclusion, the medical evidence and claimant’s testimony depict án individual who cannot sit, stand or walk for any length of time without severe pain, and who must alternate periods of sitting, standing and walking throughout the course of each day. “A man who cannot walk, stand or sit for over one hour without pain does not have the capacity to do most jobs available in the national economy.” Delgado v. Heckler, 722 F.2d 570, 574 (9th Cir.1983).
The evidence introduced relative to Gallant’s ability to perform work-related activities indicates that although no psychiatric disability limits his ability to understand, carry out and remember instructions, restriction of his daily activities and ability to respond to customary work pressures is severe due to his persistent, severe and unremitting pain. The reports show that claimant is not a malingerer and is severely and genuinely disabled. The only reports which directly support a finding of Gallant’s ability to engage in light and sedentary levels of exertion were made by two staff physicians who never examined claimant, but who based their conclusions on a review of submitted medical evidence. “A report of a non-examining, non-treating physician should be discounted and is not substantial evidence when contradicted by all other evidence in the record.” Millner v. Schweiker, 725 F.2d 243, 245 (4th Cir.1984).
The reports of the physicians who did examine claimant, which were submitted relative to Gallant’s work-related ability, are persuasive evidence of claimant’s disability due to pain and his inability to engage in any form of gainful activity. Although the AU is not bound by expert medical opinion on the issue of disability, he must give clear and convincing reasons for rejecting such an opinion where it is uncontradicted. Montijo v. Secretary of Health & Human Services, 729 F.2d 599, 601 (9th Cir.1984); Rhodes v. Schweiker, 660 F.2d 722, 723 (9th Cir.1981). While the AU mentioned these opinions, he did not set forth any specific reasons for rejecting their uncontroverted conclusions.
Thus, because the reports of the non-examining physicians were contradicted by all other evidence in the record, the medical evidence relied on below to support the Secretary’s determination that Gallant can engage in light and sedentary forms of gainful employment does not constitute substantial evidence that claimant has the residual capacity to perform the levels of exertion required under the Secretary’s definition of “light and sedentary” work.
The ALJ found Gallant’s allegations of disabling pain not credible or convincing. In making this determination, the ALJ stated he considered claimant’s testimony, the objective medical evidence, claimant’s daily *1455activities and claimant’s demeanor at the hearing. While the AU can disregard a claimant’s self-serving statements, to do so they must be unsupported by objective findings. Maounis v. Heckler, 738 F.2d 1032, 1034 (9th Cir.1984). Additionally, this circuit has accepted “the validity of the proposition that subjective symptoms of pain are a significant factor to be weighed in determining whether there exists ‘disability’ as defined in the Act.” Mark v. Celebrezze, 348 F.2d 289, 292 (9th Cir.1965).
The AU, in discrediting Gallant’s complaints of pain, referred to the fact Gallant was not currently taking pain medication and had taken pain medication only intermittently in the past. The AU failed to note, however, that one Dr. Sanders on August 19, 1981 specifically recommended claimant continue on no medication (claimant took Empirin from 1978 to November, 1980, but stopped due to its side effects). Muscle relaxants were prescribed while claimant was a patient at St. Joseph’s Hospital, which claimant has been taking twice a day since that time. The AU also found that claimant’s testimony regarding his daily activities was consistent with a light level of exertion, noting that claimant reads for long periods of time, watches television and socializes. In his testimony, claimant indicated he reads while laying down on the couch and that he could not watch a television program from beginning to end in a seated position, but must lay down or lean up against a counter with his legs apart.
Both the AU and the district judge placed emphasis on the fact that during claimant’s in-patient stay at the pain clinic at St. Joseph’s Hospital he repeatedly declined participation in the occupational therapy program. Our review of the evidence indicates that claimant did not attend the occupational therapy sessions but did come into the therapy area and socialize while there. He could not sit however, for more than a few minutes at a time, and was in pain even when engaged in conversation. When asked why he was not involved in occupational therapy, claimant stated he was unable to sit and that after attending a group therapy session for an hour he had to stand and walk about.
On this, and other less significant medical evidence, the AU concluded that Gallant’s claim of inability to work was unpersuasive and unsupported by substantial evidence. However, every medical report forming the basis of this record notes Gallant’s complaints of persistent back pain. Further, the record is replete with objective clinical findings which support and confirm claimant’s allegations of severe and chronic pain. There was no positive evidence that claimant was not suffering as much pain as he claimed to suffer. No witness, qualified expert or otherwise, expressed the opinion that claimant was in any way malingering.
The AU in part based his rejection of the objective medical evidence and the claimant’s subjective complaints of constant pain on Gallant’s demeanor at the hearing, noting that he sat for over an hour without any apparent distress. The fact that a claimant does not exhibit physical manifestations of prolonged pain at the hearing provides little, if any, support for the AU’s ultimate conclusion that the claimant is not disabled or that his allegations of constant pain are not credible. Day v. Weinberger, 522 F.2d 1154, 1156-57 (9th Cir.1975). No clear and convincing reasons were provided by the AU for his rejection of the testimony of Gallant regarding his constant and persistent back pain.
The AU’s decision as to whether a claimant is disabled must be upheld if it is based on substantial evidence. But in determining whether there is substantial evidence to support the AU’s finding, a reviewing court must consider both evidence that supports, and evidence that detracts from, the examiner’s conclusion. “We cannot affirm the examiner’s conclusion simply by isolating a specific quantum of supporting evidence.” Day v. Weinberger, 522 F.2d at 1156.
Here, there were both subjective and supporting objective clinical evidence of pain, but the AU nevertheless rejected *1456both. Although it is within the power of the Secretary to make findings concerning the credibility of a witness and to weigh conflicting evidence, Rhodes v. Schweiker, 660 F.2d 722, 724 (9th Cir.1981), he cannot reach a conclusion first, and then attempt to justify it by ignoring competent evidence in the record that suggests an opposite result. Whitney v. Schweiker, 695 F.2d 784, 788 (7th Cir.1982).
Viewing the record as a whole, it is clear that all doctors who examined claimant concur that claimant’s condition is a source of constant pain for him. Although claimant’s testimony of his persistent, disabling pain is corroborated by the medical reports of eleven treating physicians, the AU rejected this strong evidence in favor of insubstantial evidence — i.e., the report of non-treating, non-examining physician, combined with the AU’s own observance of claimant’s demeanor at the hearing. Therefore, the AU’s finding that Gallant’s allegations of severe pain do not preclude substantial gainful activity is not supported by substantial evidence.
The testimony of the vocational expert in this case cannot constitute substantial evidence to support the AU’s findings. A vocational expert’s testimony in a disability benefits proceeding “is valuable only to the extent that it is supported by medical evidence.” Sample v. Schweiker, 694 F.2d 639, 643-44 (9th Cir.1982). The hypothetical question asked of the vocational expert in this case specifically excluded pain as a limitation to Gallant’s exertional capabilities. Because claimant’s allegations of persistent disabling pain are supported by the medical evidence in this case and the AU had no clear or convincing reasons for rejecting such claims, claimant’s pain should have formed a part of the AU’s question to the expert. “[A] hypothetical question should ‘set out all of the claimant’s impairments.’ ” Baugus v. Secretary of Health & Human Services, 717 F.2d 443, 447 (8th Cir.1983) quoting O’Leary v. Schweiker, 710 F.2d 1334, 1343 (8th Cir.1983). If the assumptions in the hypothetical are not supported by the record, the opinion of the vocational expert that claimant has a residual working capacity has no evidentiary value. The most appropriate way to insure the validity of the hypothetical question posed to the vocational expert is to base it upon evidence appearing in the record, whether it is disputed or not. That procedure was not followed in this ease. Rather, the expert was asked to assume claimant’s physical capabilities conformed to those of one with the ability to perform the categories of light and sedentary work. Unless there is record evidence to adequately support this assumption, the opinion expressed by the vocational expert is meaningless. Here the vocational expert was not instructed to consider either Gallant’s constant pain or his need to alternate periods of sitting and standing. When cross-examined, the vocational expert admitted that if claimant in fact suffered from constant, severe pain, it would preclude him from all work activity. Because neither the hypothetical nor the answer properly set forth all of Gallant’s impairments, the vocational expert’s testimony cannot constitute substantial evidence to support the AU’s findings.
b. Medical-Vocational Guidelines
Gallant also asserts that the AU improperly applied Appendix 2 of the medical-vocational guidelines in this case. Although claimants have the burden of proving disability, once they show that their impairment prevents them from doing their previous job, the burden of going forward with the evidence shifts to the Secretary. Thompson v. Schweiker, 665 F.2d 936, 939 (9th Cir.1982). The Secretary must show that claimants can do less demanding substantial gainful work, given their age, education, and work experience. To meet this burden, the Secretary may rely on the medical-vocational guidelines in certain circumstances. 20 C.F.R. pt. 404 subpart P, app. 2. See Heckler v. Campbell, 461 U.S. 458, 103 S.Ct. 1952, 1954, 76 L.Ed.2d 66 (1983).
The guidelines describe only “major functional and vocational patterns,” 20 C.F.R. pt. 404, subpart P, app. 2, § 200.-00(a), and if the medical-vocational guide*1457lines “fail accurately to describe a claimant’s particular limitations, the Secretary may not rely on them alone to show the availability of jobs for that claimant.” Stone v. Heckler, 722 F.2d 464, 468 (9th Cir.1983). The AU found that Gallant had the residual functional capacity to perform light and sedentary work and applied Medical-vocational Rule 202.19 and Rule 202.17 which the AU concluded mandated a finding of “not disabled.” 20 C.F.R. pt. 404, subpart P, app. 2, §§ 202.17, 202.19. However, based on claimant’s persistent back pain, which prevents him from prolonged periods of sitting (not over 10 minutes without pain), or standing (not over half an hour), and necessitates that he alternate periods of sitting, standing, and walking, claimant argues his exertional capabilities fall between ranges of work and therefore Appendix 2 was improperly applied in this case.
To provide adjudicative guidance when a claimant’s limitations do not meet a defined exertional capacity, the Secretary issued a “Program Policy Statement.” SSR 83-12 Unempl.Ins.Rep. (CCH) (New Matters) H 14,533 (1983). Under the heading “Special Situations,” the statement discusses the impact of a finding that the claimant must alternate periods of sitting and standing. Such a claimant is defined as functionally not capable of doing either the prolonged sitting contemplated in the definition of sedentary work or the prolonged standing or walking contemplated for most light work. Because the occupational base is greatly reduced, the AU is directed to consult a vocational expert in such cases. Although the AU in this case did correctly avail himself of the testimony of a vocational expert, he still erred in applying Appendix 2 to Gallant’s ease because, as discussed above, the vocational expert was not instructed to consider this additional impairment (i.e., that claimant must alternate periods of sitting and standing) nor the constant low back pain of claimant. Therefore, the testimony by the vocational expert in this case did not constitute substantial evidence sufficient to support the AU’s finding that Gallant was able to engage in light and sedentary forms of substantial gainful employment.
CONCLUSION
The Secretary did not meet her burden of proving that claimant was capable of performing light and sedentary forms of gainful employment and the decision of the AU is reversed. This court finds the AU’s characterization of claimant’s residual capacity as capable of light and sedentary work unsupported by substantial evidence.
Because we find substantial evidence in the record as a whole supporting that Gallant is disabled within the meaning of the Act, we need not remand the case to the AU for further proceedings. Therefore, we reverse the judgment of the district court and remand with instructions that a judgment be entered awarding disability benefits to the claimant.
REVERSED.
. Light work is defined in section 404.1567(b) of title 20 of the Code of Federal Regulations as follows:
(b) Light Work. Light work involves lifting no more than 20 pounds at a time with frequent lifting or carrying of objects weighing up to 10 pounds. Even though the weight lifted may be very little, a job is in this category when it requires a good deal of walking or standing, or when it involves sitting most of the time with some pushing and pulling of arm or leg controls. To be considered capable of performing a full or wide range of light work, you must have the ability to do substantially all of these activities. If someone can do light work, we determine that he or she can also do sedentary work, unless there are additional limiting factors such as loss of fine dexterity or inability to sit for long periods of time.
As demonstrated by the above definition, light work involves frequent lifting or carrying of objects weighing up to ten pounds. Because "frequent” means occurring from one-third to two-thirds of the time, the full range of light work requires standing or walking for up to two-thirds of the workday. SSR 83-10 Unempl. Ins.Rep. (CCH) (New Matters) ¶ 14,531.