Treatment of ACL tears is controversial. Recent reports on nonoperative treatment have shown poor results. Results after primary repair have deteriorated with time, leading to augmentation procedures that seem to have improved the results. However, there have been few prospective, randomized studies in this field. Our goal was to compare primary repair with a bone-patellar tendon-bone augmentation method and with a new method using the Kennedy Ligament Augmentation Device. One hundred fifty patients aged 16 to 50, all of whom had acute ACL tears, were randomized with the closed envelope method to one of three groups treated with open surgical methods. Fifty patients were treated with primary repair, 50 patients with patellar tendon augmentation, and 50 patients were augmented with the Kennedy Ligament Augmentation Device. All patients were operated on within 10 days of injury. The rehabilitation protocol was identical, consisting of a long leg cast for 2 weeks, followed by a brace with no weight-bearing and limited motion for 6 weeks. The patients were followed prospectively by one surgeon (LE) using the Lysholm functional score, Tegner activity level score, clinical evaluation and KT-1000 arthrometer at 6 months, 1, and 2 years. Three patients were lost to followup. There was no age or activity level difference between the groups. Sport activities led to 85% of the injuries, with skiing, soccer, and European handball representing 80% of injuries. All three groups reduced their activity level the 1st year. The repair group remained at the same level after 2 years.(ABSTRACT TRUNCATED AT 250 WORDS)