The purpose of this study is to evaluate the results of primary repair and autogenous tendon augrnentation for acute rupture of anterior cruciate ligament. We primarily repaired 13 cases of acute ACL injury with autogenous tendon augmentation between Jul. 1988 and Jan. 1996. Among 13 cases, there were 2 isolated ACL injuries and 11 cases were combined with MCL injuries. All 13 cases were followed up over 1 year. An average follow up period was 4.1 years (1.1 - 8). All patients had open primary rnultiple suture repair and semitendinosus tendon (11 cases) or iliotibial band (2 cases) augmentation at average 3.6 days after the injury. In 11 cases, medial collateral ligarnent injuries were noted and these ruptured ligaments were supplemented with staple or vicryl suture. We evaluated the results with Lysholm Knee Score, KT-1000 arthrometer, postoperative ROM of knee, thigh muscle atrophy, extension lag, Lachman and pivot shift test. The clinical results were as follows 1. Lysholm Knee Score was mean 87.2 points; over 90 points: 5 cases, 80-8$ points: 5 cases, 70-79 points: 3 cases 2. Using the KT-1000 arthrometer, the average side to side difference wm 1.8nun in 201b (89N) and the compliance index was average 1.7mm. 3. Postoperative ROM of knee was nearly normal and there was no extensioe lag in any cases. But, we performed arthroscopic adhesiolysis in one case for limited motion of knee joint a ( postoperative 8 months. Thigh circumference was measured 0.95 cm difference than the healthy side at 10cm above upper pole of patella. 4. Lachman test was positive in 2 cases. 5. Pivot shift test was positive in 2 cases. Even if not many cases, we obtained relatively satisfactory results. So the pirimary repair with autogenous tendon auynentation was recornmandable procedure for acute rupture of ACL, especially combined with MCL injury.