PURPOSE: This study was performed to analyze the significant factors that may affect failure of fixation in trochanteric fractures of the femur treated with the compression hip screw. MATERIALS AND METHODS: From May 1995 to July 2000, the authors analyzed 97 cases of trochanteric fracture of the femur treated with the compression hip screw and followed more than one year. We classified the fracture type by Jensen 's method. We used Singh index for the degree of osteoporosis. In the post-operative radiograph, we checked neck-shaft angle, state of reduction, position of the lag screw within the femoral head, tip-apex distance, and sliding distance of the lag screw. The relationship between these factors and failure of fixation was statistically analyzed. RESULTS: There were 17 cases (17.5%) of failure of fixation ; 15 cases (15.4%) of excessive sliding of the lag screw, 1 case (1%) of cutting out of the lag screw, and 1 case (1%) of valgus malunion. There were significant relationships between failure of fixation and old age over 80, unstable fracture, telescoping reduction, anterior or medial displacement of the distal fragment, and anterior placement of the lag screw within the femoral head. CONCLUSION: Accurate reduction and avoidance of the placement of the lag screw in the anterior part of the femoral head were important factors to prevent failure of fixation in trochanteric fractures of the femur treated with the compression hip screw.