The acute anterior cruciate ligament injury is one of the most common ligament injury of the knee joint and there are many controversies in its treatment. Warren reported that the primary repair for the acute anterior cruciate ligament injuries was good, but some had opposite oppinions. Authors studied 23 patients of actue anterior cruciate ligament injury who were treated by primary repair from January, 1982 to December, 1984. The results were as followings: 1. The most common associated injury was MCL injury and posteromedial capsular injury(13 cases; 56.5%). 2. The most common detachment site of ACL was femoral attachment(11 cases; 47.8%). 3. A medial Hocky Stick incision was found good in repairing the combined MCL and posteromedial capsular tear with ACL injury. 4. The results were good in 74% by Cincinnati score and in 87% by objective score. It is concluded that primary repair of the acute anterior cruciate ligament tear is cosidered successful.