ACL plays an important role in stability of knee joint and its injury causes instability of joint which is known as the initiation of problem knee. Reconstruction of the anterior cruciate ligament would be preferred to the primary repair in treatment. And recently with the advance of arthroscopic technique and development of bone-patellar tendon-bone (BPB) graft material, the result of reconstruction is somewhat superior to that of primary repair. Authors compared the results of 20 primary repairs (Group I ) and 20 reconstructions (Group II) among 64 acute ACL injury treated Sung-Ae General Hospital from January 1989 to December 1994. The results were as follows: 1. Most common associated injuries were medial collateral ligament rupture and medial meniscal tear. 2. Group I showed postoperatively 13 negative anterior drawer test, 12 negative Lachmann test and 12 negative pivot shift test and group II showed postoperatively 17 negative anterior drawer test, 15 negative Lachmann test and 17 negative pivot shift test. (p<0.05) 3. In postoperative Lysholm knee scoring scale, group I showed 86 points and group II showed 93 points (p<0.05). 4. In postoperative KT-1000 arthrometer, 12 cases in Group I and 16 cases in Group II showed less than 2mm difference with sound side (p<0.05).