The purpose of this study was to compare the effects of biofeedback-facilitated exercise with exercise alone on the recovery rate of quadriceps femoris muscle function following anterior cruciate ligament (ACL) reconstruction. Functional measures included 1) a dynamometric test of quadriceps femoris muscle isometric peak torque during the 12th postoperative week and 2) the number of days post-operatively that a patient achieved full active extension of the knee. Twenty-two patients with acute ACL injury were randomly assigned to a Treatment (biofeedback) Group (n = 11) or a Control (nonfeedback) Group (n = 11) during the first therapy session one week after reconstructive surgery. After the patients had completed the 12-week exercise program, the quadriceps femoris muscle isometric peak torque in the operative limb was compared with that in the nonoperative limb at three angles (90 degrees, 60 degrees, and 45 degrees) of extension. An analysis of variance revealed significant differences between the Treatment and Control Groups at all three angles. Mean recovery time was calculated for each group, and a t test for independent samples indicated a significant difference between the groups. These results demonstrate that the addition of biofeedback to muscle strengthening exercises facilitates the rate of recovery of quadriceps femoris muscle function following ACL reconstruction.