The posterior cruciate ligament(PCL) is one of the most important structures in the knee joing because it provides about 94% of the total restraint to posterior displacement of the tibia & posterior stability of the knee joint. If the posterior instability persisted, rotational instability, injury to meniscus and degenerative change develop within several years. The purpose of this study is to know the result of the posterior cruciate ligament reconstruction using semitendinosus tendon and to know the factors which affected to good result. During the period from January 1989 to December 1994, 16 cases with posterior cruciate ligament reconstruction using semitendinosus tendon were evaluated clinical and radiological results retrospectively and performed stastical analysis using the SPSS. The results were as follows; 1. The average preoperative posterior laxity was 14.1 mm and average postoperative laxity was 6.3 mm. It was improved 7.8 mm. 2. In other associated injured ligament group with or without fracture, above good was in 8 cases and below fair in 6 cases, but there was no significant difference between the two (X²=9.8, df=1, P>0.05). 3. In the poor result group, mean body weight was 80(±13.23)kg and there was significant difference between poor group & fair, good, excellent group(F=3.52, P<0.05). From these results it would be suggested that PCL reconstruction using semitendinosus tendon is more effective in relatively light weighted group than heavier group.