Clint Smith, a sixty-four year old man with an eighth-grade education, applied for disability insurance benefits, alleging that he cannot work because he suffers from arthritis, back pain, an ulcer, liver cirrhosis, and hypertension. An Administrative Law Judge (“ALJ”) concluded that Mr. Smith did not have a disability as defined under the Social Security Act,.and that his skills and residual functional capacity allowed him to perform a significant number of jobs in the national economy, including that of a forklift operator. The Appeals Council denied Mr. Smith’s request for review, and the district court affirmed. On appeal, Mr. Smith (now limiting his claim primarily to arthritis and hypertension) argues that the ALJ made flawed credibility determinations, ignored evidence of his arthritis, and improperly credited the opinion of a consulting physician over that of his own treating physician. Because the ALJ’s decision is not supported by substantial evidence, we reverse.
I.
Mr. Smith worked for twenty-four years as a supervisor at a plating company, where he operated a conveyor belt, ran a forklift and completed reports. After he was laid off in 1984, Mr. Smith worked for the City of Chicago for about three months in 1986 or 1987 while on “public aid,” and in 1988 he was awarded disability insurance benefits due to alcoholism.
*435After a 1996 amendment to the Social Security Act eliminated alcoholism as a basis for obtaining disability insurance, see Pub.L. 104-121, the Social Security Administration (“SSA”) notified Mr. Smith that his benefits would cease in January 1997 unless he could show that he continued to be disabled and that his alcoholism was not a contributing factor to his disability. Mr. Smith requested a review of the notification, claiming that he was unable to work because of arthritis throughout his body, a bad back, an ulcer, and cirrhosis of the liver.
According to the treatment notes of Dr. James Baraglia, Mr. Smith’s treating physician since 1978, Mr. Smith began in 1985 to complain of pain in his right ankle, left knee, shoulders and back. Dr. Baraglia diagnosed arthritis. X-rays taken in 1987 indicated early degenerative disease and loose calcification in Mr. Smith’s left knee and possible calcification or old trauma in his right ankle. A 1989 X-ray revealed no arthritic changes in Mr. Smith’s left shoulder. No references to pain or arthritis appear to have been recorded between 1991 and 1995, but in 1996, osteoarthritis was noted under the “problem list” portion of Dr. Baraglia’s progress notes for Mr. Smith. Dr. Baraglia prescribed non-aspirin for Mr. Smith’s pain, noting that Mr. Smith should avoid prescription “NSAID’s” (nonsteroidal anti-inflammatory drugs used to relieve pain, stiffness, and inflammation) because of previous gastrointestinal bleeding. Most recently in November 1996, the doctor prescribed medication for hypertension.
After Mr. Smith requested a review of SSA’s notification that his benefits would cease, he was examined by Dr. Sanjay Bharti, a consultative physician, in August 1996. Dr. Bharti observed that Mr. Smith had no limitation of movement except in his right ankle, which was slightly everted (turned out). The doctor noted that Mr. Smith walked on only half of his right foot, but he had a normal gait and could walk on his heels and toes. An X-ray revealed mild to moderate degenerative changes in his right ankle. The rest of Mr. Smith’s joint movements, Dr. Bharti observed, were normal, and he was able to “do his daily living without much of a problem.” Dr. Bharti noted that Mr. Smith could squat and touch his toes, and was able to put on his clothes relatively quickly. Although Mr. Smith indicated that he had back pain if he bent over, lifted anything over 50 pounds, or if he sat or stood too long, Dr. Bharti observed that Mr. Smith had full range of motion in his back. He likewise noted normal strength and no sensory deficit to pinprick or touch.
Also in August, state agency physician Dr. Victoria Dow assessed Mr. Smith’s residual functional capacity based on Dr. Bharti’s examination. Dr. Dow opined that Mr. Smith had mild degenerative joint disease (osteoarthritis) in his ankle and his range of motion was reduced in that area, but that his daily activities were not significantly restricted. She also opined that Mr. Smith had probable degenerative joint disease in the lumbar area, but that he had a normal range of motion in his lower back. Dr. Dow concluded that Mr. Smith could occasionally lift and/or carry up to 50 pounds and frequently lift and/or carry up to 25 pounds, and that he could stand and/or walk and sit (with normal breaks) about six hours in an eight-hour workday.
Four months later in December 1996, Dr. Baraglia completed an assessment of Mr. Smith’s physical ability to do work-related activities. Dr. Baraglia estimated Mr. Smith’s capabilities more conservatively than Dr. Dow, opining that Mr. Smith could occasionally lift only 20 pounds because of arthritis in his shoulders and left elbow. Further, Dr. Baraglia opined that Mr. Smith could not stand or walk at all in an eight hour workday, and only occasionally could climb, balance or stoop due to arthritis in his knees. Dr. Baraglia also determined that Mr. Smith had no sitting limitation, but limited Mr. Smith’s abilities to reach, handle, push, and pull because of his arthritis.
*436Two months later in February 1997, Dr. Baraglia completed another questionnaire as to Mr. Smith’s physical residual functional capacity, this one opining that Mr. Smith could not walk even one block without rest or severe pain. Dr. Baraglia’s February assessment also opined that Mr. Smith could occasionally lift and carry no more than 10 pounds, and indicated that he could stand, walk and sit about four of eight hours intermittently, but no more than one hour at a time. Dr. Baraglia also opined that Mr. Smith could bend and twist only 20 percent of the day, a significant decline from Dr. Bharti’s observation that he had full range of motion in his back.
At a hearing before the ALJ in April 1997, Mr. Smith testified that he was unable to work because of arthritis, particularly in his shoulders and neck, and that his knee was “shot.” He told the ALJ that he has had an everted right ankle all his life. According to Mr. Smith, he had severe pain 2 or 3 times a week at night when he was laying down, and took six extra-strength non-aspirin a day to lessen the pain. He testified that he was taking medication for hypertension that controlled his high blood pressure “most of the time,” but he still became “woozy” about 2 or 3 times a week when he bent over.
Mr. Smith told the ALJ that he could stand for 20 to 25 minutes at a time, and walk 3 to 4 blocks when he felt like it. He also was able to sit for 25 to 30 minutes before standing up to avoid getting stiff. Mr. Smith testified that he could regularly lift 15 to 20 pounds with one hand and 25 to 30 pounds with both, but had problems lifting anything heavier than 50 pounds. He told the ALJ that he lived alone in a first-floor apartment, and could bathe, feed and dress himself, do his own grocery shopping, do his laundry, cook and clean his apartment.
Also at the hearing, a vocational expert (“VE”) testified about the number of jobs available for someone with Mr. Smith’s skills and limitations. The VE testified that Mr. Smith’s past work was heavy in physical demand and semi-skilled. In response to a hypothetical question posed by the ALJ, the VE explained that if Mr. Smith had the limitations set forth in either of Dr. Baraglia’s December 1996 or February 1997 assessments, he would be limited to sedentary work, and in view of his age, eighth-grade education, and past relevant work, there would be no transferability of his skills. The VE testified, however, that although Dr. Dow’s assessment would not allow for past relevant work, it would allow for medium exertional work, and that Mr. Smith had skills readily transferable to the position of forklift operator.
After applying the five-step sequential process for evaluating if a claimant has met the burden of establishing disability, see 20 C.F.R. § 404.1520, the ALJ concluded that Mr. Smith was not disabled as defined in the Social Security Act. The ALJ found that Mr. Smith had not been gainfully employed since January 1985. The ALJ next determined that Mr. Smith had a severe “inverted” right foot, hypertension without evidence of end-organ damage, and mild hearing loss in the left ear;1 however, he did not have an impairment or combination of impairments listed in or medically equal to one listed in 20 C.F.R. pt. 404, subpt. P, app. 1. The ALJ further concluded that Mr. Smith was unable to perform his past relevant work as a planing factory supervisor, but his residual functional capacity allowed him to perform medium work, except for lifting in excess of 50 pounds occasionally and 25 pounds frequently, or working in environments *437where he would be exposed to more than mild noise levels. The ALJ found that although his additional nonexertional limitations precluded Mr. Smith from performing the full range of medium work, there were a significant number of jobs in the national economy that he could perform, notably that of a forklift operator.
In analyzing Mr. Smith’s capacity to work, the ALJ discredited Mr. Smith’s complaints of pain. The ALJ observed, for instance, that his claimed levels of pain and functional limitation were not borne out by the clinical signs and findings. The ALJ also noted inconsistencies within Mr. Smith’s testimony as well as inconsistencies between his testimony and statements he made to Dr. Bharti. The ALJ also discounted Mr. Smith’s treating physician’s (Dr. Baraglia) two assessments of Mr. Smith’s capacity to work because they were mutually inconsistent and unsupported by the clinical signs and findings, and concluded that the doctor was “leaning over backwards to favor his patient.”
Mr. Smith appealed the ALJ’s adverse decision. The Appeals Council denied Mr. Smith’s request for review. Mr. Smith then filed a complaint in the district court. After the parties filed cross-motions for summary judgment, a magistrate judge, presiding with the parties’ consent, granted the Commissioner’s motion and denied Mr. Smith’s. The magistrate judge concluded that substantial evidence in the record supported the ALJ’s findings.
II.
On appeal, Mr. Smith confines his claimed disability to arthritis-induced pain in his right ankle, knees, shoulders and elbow, as well as dizziness caused by hypertension. He argues that the ALJ’s decision is not supported by substantial evidence because the ALJ made flawed credibility determinations, erroneously made an independent medical determination that he did not suffer from arthritis, and failed to properly weigh the medical opinions pursuant to 20 C.F.R. § 404.1527(d). We agree.
Because the Appeals Council found no basis for further review, the ALJ’s findings constitute the final decision of the Commissioner of the SSA. See Luna v. Shalala, 22 F.3d 687, 689 (7th Cir.1994). We will affirm an ALJ’s decision only if it is supported by substantial evidence, which is evidence “a reasonable mind might accept as adequate to support a conclusion.” See Powers v. Apfel, 207 F.3d 431, 434 (7th Cir.2000) (quoting Diaz v. Chafer, 55 F.3d 300, 305 (7th Cir.1995)).
We are troubled by the ALJ’s credibility findings in this case. The ALJ discounted the functional limitations set forth by Mr. Smith’s treating physician, Dr. Baraglia, because they were “not based on persuasive or even reasonable evidence.” In particular, the ALJ pointed out that Dr. Baraglia failed to order X-rays to confirm the presence of arthritis. The failure to order X-rays, however, is not an appropriate basis to wholly discredit Dr. Baraglia’s opinion. The ALJ disregarded evidence that as early as 1987, X-rays had revealed that Mr. Smith was experiencing the onset of degenerative disease in his knee. Over the course of nearly ten years, this “early” degeneration would presumably have advanced, as X-rays of Mr. Smith’s ankle taken in 1987 and 1996 had indicated. If the ALJ was concerned that the medical evidence was insufficient to determine whether Mr. Smith was disabled, he should have ordered more recent X-rays. See 20 C.F.R. § 404.1517.
Although a claimant has the burden to prove disability, the ALJ has a duty to develop a full and fair record. See Thompson v. Sullivan, 933 F.2d 581, 585 (7th Cir.1991). Failure to fulfill this obligation is “good cause” to remand for gathering of additional evidence. Id. at 586. We fail to see how the ALJ could have properly assessed the extent of Mr. Smith’s arthritis without more updated X-rays. Given that the most current X-rays *438of Mr. Smith’s knee were taken nearly ten years before the hearing and revealed the early stages of degenerative disease, it was incumbent upon the ALJ to order additional X-rays to ascertain the extent of the degeneration of Mr. Smith’s knee. See id. at 587 (“[g]iven that the last x-rays of [the claimant’s] spine were taken in December of 1978, the ALJ’s duty to sufficiently develop the record [by 1987] would suggest the need to order additional x-rays or other imaging tests to ascertain the extent of degeneration of [the claimant’s] back and neck”). For the same reason, we disagree with the ALJ that the absence of objective clinical findings was a sufficient basis not to afford Dr. Baraglia’s opinion controlling weight. See 20 C.F.R. § 404.1527(d)(2).
Mr. Smith also argues that the ALJ failed to explicitly consider the effect of his hypertension-induced dizziness on his ability to work. By November 1996, Mr. Smith’s blood pressure had risen to such a degree that his doctor had prescribed medication. The ALJ found that Mr. Smith suffered from “hypertension without evidence of end-organ damage,” yet never commented as to any less damaging but nonetheless significant effects of hypertension, if any, on Mr. Smith’s suitability as a forklift operator. Indeed, there is no indication that the VE ever considered dizziness as a possible impediment to safe operation of a forklift; the ALJ inquired only as to Mr. Smith’s employability in view of the functional limitation assessments provided by Drs. Baraglia and Dow. The ALJ’s failure to consider the evidence of dizziness alone precludes us from “evaluating] ... whether substantial evidence existed to support the ALJ’s finding,” see Herron v. Shalala, 19 F.3d 329, 334 (7th Cir.1994) (remanding case where ALJ failed to consider evidence relating to claimant’s hand impairment), but we are also troubled by the ALJ’s failure to address the VE’s testimony that a forklift required “frequent to constant” use of his right ankle to operate the foot controls, in view of Mr. Smith’s most recent X-ray indicating mild to moderate degeneration in that precise area. See DeFrancesco v. Bowen, 867 F.2d 1040, 1044 (7th Cir.1989) (remand warranted where ALJ deemed claimant’s occasional confusion of brake with gas pedals due to numb feet only slight restriction on ability to work). An ALJ may not simply select and discuss only that evidence which favors his ultimate conclusion. See Herron, 19 F.3d at 333. Rather, an ALJ’s decision must be based upon consideration of all the relevant evidence. Id. Accordingly, we ReveRse the district court’s decision granting summary judgment in favor of the Commissioner and Remand the case for further consideration consistent with this opinion.
. In August 1986, Mr. Smith was diagnosed with moderate sensoneural hearing loss in his right ear, with normal hearing at 4 kilohertz. Mr. Smith testified at the hearing that he has a problem with “roaring” in his right ear, but that he still could hear the TV, radio and conversation.