PURPOSE: To analyze the factors predisposing to complications after internal fixation of femoral neck fracture. MATERIALS AND METHODS: We reviewed retrospectively the results of percutaneous internal fixation of femoral neck fracture using multiple pinning, in 52 cases who were treated from Jan. 1996 to Dec. 2001. Relationship between the complications and several factors such as the age, sex, time interval from injury to operation, Garden stage, Singh index, internal fixation device and state of redction were analyzed. RESULTS: The functional results by Lunceford criteria were excellent in 23 cases (44%), good in 15 cases (29%), fair in 2 cases (3.8%) and poor in 12 cases (23.1%). The avascular necrosis of the femoral head were occured in 14 cases (26.9%). Among these, 1 case of non-union, 2 cases of mal-union were accompanied. No stastically significant relationship between the age, sex, time interval from injury to operation, Garden stage, Singh index, internal fixation device, state of redction and complication. However, there was 4 times higher complication rate in Garden stage 3 or 4 group than its rate in Garden stage 1 (odds ratio 3.889), and 3 times higher complication rate in non-anatomical reduction group (odds ratio 3.22). CONCLUSION: Factors predisposing to complications after internal fixation of femoral neck fracture seemed to closely relate with Garden stage and state of reduction.