We report for the first time a reconstructive procedure of the posterolateral complex using allograft tissue to restore fibular collateral ligament function. The procedure is designed for knees where insufficient soft tissues are present and suitable autogenous graft tissues are not available. Twenty consecutive patients were studied; all returned for follow-up evaluation a mean of 42 months (range, 24 to 73) after surgery. The results were evaluated with the use of a comprehensive subjective and objective system that rated 20 factors. The success rate for the operative procedure was 76% (16 of 21 operations) as judged by knee stability examination and stress radiographs. Three of the reconstructions showed partial stretching and two failed. There was significant improvement from preoperative to follow-up scores of functional limitations in sports activities (P < 0.05), symptoms (P < 0.01), and overall scores (P < 0.0001). The immediate knee motion and rehabilitation program restored 0 degrees to 135 degrees of motion in all knees and was not deleterious to the reconstructions.