The posterior cruciate ligament plays as basic stabilizer of the knee. Therefore the knee becomes unstable when tibial insertion of the posterior cruciate ligament is avulsed. The diagnosis may be delsyed or missed because of surgeon's 1sck of awareness or rare condition. The authors treated seven cases of avulsion fracture of posterior cruciate ligsment at the tibial attachment ares ranged from ten to thirty-two years. There were five male and two female. The results were as follows : 1. The cause of all seven cases injury was traffic accident. 2. The physical findings were seven positive posterior drawer test, seven cases of abrasion or laceration over the anterior proximal tibial surface and antero-medial surfsce of the knee joint. 3. The associated injury was comminuted fracture of the tibia and femur (1 case), rupture of collateral ligsment and comminuted fracture of the tibia (1 case) and zygomatic fracture (1 case). 4. The treatment methods were four cancellous fixation, one K-wire fixation after epiphyseal plate fusion but each one pull out wire and dexon suture before epiphyseal plate fusion. 5. The motion of knee joint was within normal limit and no instsbility was inspected at the three months after reduction.