The posterior cruciate ligament in the stoutest ligamentous structure in the knee joint. Kennedy and Hawkins have confirmed its strenght to be about 2 times that of the anterior cruciate ligament or tibial collateral ligament. This would appear to offer the support that this ligament has a vital role to play in knee stabilization. But, in the past, non-surgical management was frequently elected either because of the belief that most kness with posterior cruciate insufficiency are asymptomatic or because it is difficult to access surgically. Recently, Hughston and Trickey reported good results after surgical repair of the rupture of the posterior cruciate ligament. And current trend is to repair it surgically. So, we analyzed the 36 cases of acute posterior cruciate ligament injuries, who were admitted and treated surgically in Severance Hospital between Jan. 1981 to Dec. 1985, and obtained the following results. 1. Single rupture of the posterior cruciate ligament largely results in good outcome. 2. When the rupture site is in the substane, we can obtain relatively good results with the augmentation using the medial head of the gastrocnemius. 3. When combined with medial or lateral compartment injuries, the chance of later instability and reconstruction is high.