From a total of 293 patients who had an acute, complete anterior cruciate ligament rupture, we selected all patients (N = 55) who had an anterior cruciate ligament rupture without associated meniscal or ligamentous injuries, and all patients (N = 52) who had an anterior cruciate ligament rupture combined with a rupture, and subsequent primary repair, of the medial collateral ligament. Initially, all patients were assigned to one of two groups: conservative treatment of the anterior cruciate ligament or augmented anterior cruciate ligament repair with the iliotibial band. In the 52 patients who had an anterior cruciate ligament rupture combined with a medial collateral ligament rupture, the associated injuries to the medial collateral ligament and sometimes the posterior oblique ligament, meniscus, and arcuate ligament complex were treated in a similar fashion, without regard to the treatment of the anterior cruciate ligament. Ninety-nine patients (93%) were reexamined 35 to 74 months after the injury, and knee function was evaluated with subjective and objective criteria, including functional tests. Patients who had been treated with augmented anterior cruciate ligament repair had superior stability with better subjective results and returned to strenuous activities more frequently than patients who had undergone conservative treatment. In those patients who had augmented repair, the prognosis did not differ between those who had isolated lesions and those who had combined lesions. Conservative treatment of the anterior cruciate ligament with repair of the medial collateral ligament and other associated injuries, when present, resulted in an almost equally unfavorable outcome for patients with combined and isolated anterior cruciate ligament lesions.