We granted certiorari to review an unpublished decision of the court of appeals which reversed the decision of the Industrial Commission of Colorado (Commission) and remanded this workman’s compensation case for affirmation of the referee’s order. The court of appeals ruled that the issues in controversy were questions of evidentiary facts, that findings of eviden-tiary facts are binding upon the Commission unless they have no substantial support in the record, and that the evidentiary facts found by the referee did have substantial support in the record. We reverse.
*1117I.
Lenzie A. Jones, the claimant, sustained a low back injury in an accident while working for Asarco, Inc. (Asarco), in November 1975. Subsequently he had an operation for a herniated disc. Although the surgery relieved the pain in his lower back and right leg, Jones could not perform his work. He applied for workmen’s compensation benefits, and he was awarded permanent partial disability benefits of six percent as a working unit in June 1977.
After being terminated by Asarco, Jones became a welder and was employed by General Iron Works from 1978 to 1981. In early 1981, he became aware of a change in his physical condition, and a few months later he left his position with General Iron Works. In August 1981, he filed a petition with the Commission in which he sought to reopen his workmen’s compensation claim.
The petition to reopen alleged that Jones had been injured in 1975 and that his physical condition has changed “in that it has become worse.” The petition was supported by a report of Dr. Steve A. LeVally dated August 11, 1981, which stated:
Mr. Jones has been seen in our clinic recently for recurrence of long-standing low back pain, having had a lumbar lami-nectomy in 1977. For the past 2-3 months has had left lumbar pain with occasional radiation to the lateral aspect of the left leg.
Examination shows spasm of the left lumbar muscle group with good muscle tone throughout. The deep tendon reflexes are normal on the right but diminished in the left knee.
He has received some lessening of pain with physical therapy but is still fairly symptomatic. He is also being treated with bed rest, heat and muscle relaxants. He is to be reevaluated in one week.
At the request of the State Compensation Insurance Fund (Fund), the insurance carrier for Asarco, Jones was examined by Dr. Martin Anderson. In his report of October 6, 1981, Dr. Anderson made the following diagnosis:
DIAGNOSIS: Protruded lumbar inter-vertebral disc with mild symptoms following surgical treatment 1977.
Strain low back, lifting at work, June, 1981,
Scoliosis, developmental, lumbar spine, mild.
He developed some pain in the lower portion of his back working as a welder in June, 1981. He was examined and treated. His physician recommended that he rest and stay off work. The patient says he wants a release to go back to work but the doctors thought he ought to stay off for a few more weeks. Examination at this time reveals signs of postoperative surgical treatment with a generally satisfactory result. I believe that he could return to his regular job at this time. He was instructed in proper lifting and should avoid lifting objects that weigh more than forty pounds. X-rays reveal a curvature of the lumbar spine which I believe is developmental and can cause some weakening of the bony structure. I do not believe he requires further treatment at the present time. He might benefit from wearing a sacroiliac belt with pad at work. I do not believe there has been any aggravation of his pre-existing disability.
Based on Dr. Anderson’s report, the Fund took the position that Jones’s physical condition resulted from a new injury and objected to reopening the claim.
In December 1981, Dr. Stevan Goff, the claimant’s physician, reported that Jones had been evaluated on numerous occasions for lower back pain since July 1981. He stated that Jones had been examined by a neurologist whose evaluation was inconclusive for recurrent disc disease. He also said that a neurosurgeon who examined Jones felt that Jone’s back pain “represented a recurrent lumbar strain without well defined symptoms of a lumbar disc lesion.” Dr. Goff anticipated that Jones would periodically suffer from low back pain and recommended that he return to work with light duty for two to three weeks.
*1118At the hearing to reopen held in January-1982, Jones was the only witness. He testified that he first noticed a change in his condition in January 1981 and there had been no on-the-job accidents while working for General Iron Works. He stated that he was unable to do any lifting, stooping, or sitting for a prolonged time and had pain in his back and legs. He also testified that if a job required prolonged sitting or standing he was unable to perform it.
The referee, by order dated February 25, 1982, found that: (1) Jones sustained an injury in 1975; (2) he left work on July 20, 1981, because of discomfort in his low back and right leg and has been under the care of Drs. LeVally and Goff; (3) he had been released by Dr. Goff to return to work with restrictions; (4) his condition has worsened and that the worsening is not related to claimant’s employment at General Iron Works, but to his injury in November 1975. As a result of these findings, the referee concluded that the claimant’s physical condition “has worsened and that the worsening is related to the claimant’s industrial accident of November 20, 1975” and “the claimant continues to be symptomatic in his low back and right leg and has been totally disabled since July 20, 1981.” The petition to reopen was granted and temporary total disability benefits were ordered to be paid to Jones from July 20, 1981, as well as necessary medical, surgical, and hospital expenses, not to exceed $20,000.
The Fund and Asarco petitioned for review. The Commission, after reviewing the entire record, determined that “[t]he evidence is not sufficient to show a worsening of [Jones’s] condition following his recovery [from] surgery in 1977, or to show by a preponderance of evidence that the cause of his current symptoms was from the 1975 injury with its 1977 surgical treatment.” The Commission also stated that none of the three expert opinions “says that the claimant’s condition at the time of the petition to reopen was worse and was related to his prior compensable injury; and one of them opined that there was not any aggravation thereof.” The Commission reversed the referee’s decision, holding that Jones had failed to sustain his burden of showing by a preponderance of the evidence a change in condition pursuant to section 8-53-119, 3 C.R.S. (1973).
In his petition for review, Jones claimed that the Commission’s order was contrary to the law and the evidence, and that the Commission erred in making findings of evidentiary facts in conflict with the facts found by the referee. He argued that the evidence clearly reflects a worsening of the claimant’s condition and that Ch. 86, sec. 2, § 8-53-106(2)(b), 1981 Colo. Sess. Laws 4761 prohibited the Commission from modifying “the findings of fact in any way, but may only modify the Order if it is not in accordance with the findings of fact made by the Division of Labor Hearing Officer.”
The Commission rejected claimant’s argument. It .reaffirmed its initial determination that the referee’s order was contrary to the weight of the evidence. It then concluded that section 8-53-106(2)(b) preserves the Commission’s authority to find or to set aside ultimate conclusions of fact and “even in findings of evidentiary fact, the Commission has authority to act to find the facts correctly if the findings of evidentiary fact by the referee are contrary to the weight of the evidence.”
*1119The claimant appealed and the court of appeals set aside the Commission’s order and remanded the case for affirmation of the referee’s ruling. The court first found that both treating physicians, Drs. LeVally and Goff, connected Jones’s 1981 symptoms to his 1977 surgery. It then held that the referee’s findings that Jones’s condition had worsened and the worsening was attributable to his 1975 work-related injury were findings of evidentiary facts, and such findings are binding upon the Commission unless they have no substantial support in the record. It then concluded that, given the substantial evidence supporting the referee’s determinations, it was error for the Commission to set these findings aside.
The Commission, Asarco, and the Fund sought certiorari review by this court. We granted certiorari to determine whether the Commission applied the proper standard of review in setting aside the referee’s finding and reversing his decision to allow Jones to reopen his claim.
II.
The Commission’s standard of review over a referee’s findings is controlled by section 8-53-106(2)(b), 3 C.R.S. (1982 Supp.).2 In Baca v. Helm, 682 P.2d 474 (Colo.1984), we reviewed this statute.
In Baca the question was whether causation is an ultimate or an evidentia-ry fact. In the present case, the question is whether the Commission applied the proper standard of review in setting aside the referee’s findings and reversing his decision. Ordinarily it is necessary to determine whether findings are of evidentia-ry or ultimate facts in order to determine what the proper standard of review is. If the findings are of ultimate facts, the Commission is free to make an independent conclusion. Baca, 682 P.2d at 476; R&R Well Service Co. v. Industrial Commission, 658 P.2d 1389, 1391 (Colo.App.1983). The Commission may only set aside findings of evidentiary facts, however, if the findings are contrary to the weight of the evidence. Section 8-53-106(2)(b), 3 C.R.S. (1982 Supp.); Baca, 682 P.2d at 476. If the referee’s findings that the claimant’s condition had worsened and that the worsening was attributable to his 1975 injury were findings of ultimate facts, then the Commission had the power to set aside the referee’s decision since it is empowered to make independent conclusions regarding ultimate facts. If the referee’s findings were of evidentiary facts, however, then the Commission had the power to set aside the referee’s decision only if the findings were contrary to the weight of the evidence. In the present case, it is unnecessary to determine whether the referee’s findings were of ultimate or evidentiary facts since even assuming, arguendo, that the findings were of evidentiary facts, we agree with the Commission that the referee’s findings were contrary to the weight of the evidence.
“The statutory phrase ‘contrary to the weight of the evidence’ ... means unless the findings are not supported by a preponderance of the evidence.” Fort Logan Mental Health Center v. Industrial Commission, 665 P.2d 139, 140 (Colo.App.1983) rev’d on other grounds, Industrial Commission v. Fort Logan, 682 P.2d 1185 (Colo.1984). The preponderance standard is met when “the existence of a contested fact is ‘more probable than its nonexistence.’ ” People v. Taylor, 618 P.2d 1127, 1135 (Colo.1980).
Here, the evidence concerning the cause of Jones’s 1981 discomfort was not in conflict. Jones’s physicians never stated that his 1975 injury was the cause of his 1981 complaints, and Dr. Anderson concluded that Jones’s back pains did not arise from *1120an aggravation of his preexisting disability. Thus, even assuming the Commission’s standard of review was the more narrow standard of reviewing evidentiary facts as opposed to the standard of reviewing ultimate facts, we believe the Commission acted within its power. Our review of the record supports the Commission’s order that Jones failed to sustain his burden of showing by a preponderance of the evidence that the cause of his current symptoms was the 1975 injury. Having exercised its authority in conformity with the statutory mandate, the Commission’s order reversing the referee should not have been set aside by the court of appeals.
Accordingly, we reverse the judgment of the Colorado Court of Appeals.
QUINN, J., dissents, and KIRSHBAUM, J., joins in the dissent. NEIGHBORS, J., specially concurs in part and dissents in part and joins in Part III of Justice QUINN’s dissent.. § 8-53-106, 3 C.R.S. (1982 Supp.), states in part:
(2)(a) The commission, upon referral of a case to it by the director or upon a petition being filed with it to review the director’s or a referee's supplemental award, shall review the entire record transmitted by the director in said case and shall enter its award thereon. ...
(b) The findings of evidentiary fact, as distinguished from ultimate conclusions of fact, made by the director or referee shall not be set aside by the commission on review of the director’s or referee’s decision unless the findings of evidentiary fact are contrary to the weight of the evidence. The commission may remand the case to the director or referee for such further proceedings as it may direct, or it may affirm, set aside, or modify the order or any sanction of relief entered therein, in conformity with the facts and the law.
. The General Assembly, effective July 1, 1983, repealed and reenacted Article 53 of title 8, C.R.S., with amendments. The standard of review after July 1, 1983, set out in § 8-53-111(7), 3 C.R.S. (1983 Supp.), provides: "The commission may reverse, remand, or affirm any order [entered by the director or hearing officer].... If the findings of evidentiary fact entered by the director or hearing officer are supported by substantial evidence, they shall not be altered by the commission.”