The anterior cruciate ligament(ACL) is one of the major stabilizers of knee motion. The ACL does not heal once torn, unlike many other biological tissues. Its absence can lead to severe joint instability which can lead to disruptions of secondary restraints around the knee and then progress to degenerative joint disease. Thus many authors advocate surgical intervention for a torn ACL in order to restore stability to the joint. Yet, there is still controversy as to best treatment for the ACL injuries. It is desirable to be considered for the patients age, the severity of the injury, and the future activity level of the patient to decide treatment. We analyzed thirty ACL acute injuries of twenty seven patients who had an ACL injury and treated surgically between Apr. 1986 and Dec. 1991 at St. Pauls Hospital. The results were as follows: 1. There were twenty five males and two females. The mean age was 33.4 years ranged, 15 to 52 years. 2. The anterior cruciate ligaments were torn at proximal portion in twenty two cases, at midportion and distal portion in four, respectively. 3. Two knees had isolated ACL injuries and twenty eight had combined injuries. 4. Twenty one out of twenty six cases treated with primary repair, and three out of four cases treated with reconstruction had good-excellent results.