We analyzed failures of surgical treatment of femoral neck fractures due to osteonecrosis in a consecutive series of 26 patients with an average age of 31 (range, 10 to 49 years). These patients were referred for treatment of osteonecrosis that developed after internal fixation of a fracture of the femoral neck. The average Harris hip score at the time of referral was 59. The length of time from fracture treatment to the development of osteonecrosis averaged 22.5 months (range, 5 months to 13 years). All patients were symptomatic at the time of presentation. Internal fixation used at the time of the initial trauma included a variety of cannulated and noncannulated screws and sliding hip screws. Of the 27 fractures, 7 (26%) were nondisplaced, 20 (74%) were displaced, and 2 (7%) were open and displaced. Fifteen patients had previously had removal of hardware, making magnetic resonance imaging of the femoral head possible. Of those patients, 2 had involvement of 25% or less of the femoral head, 7 had involvement of 25% to 50%, 5 had involvement of 50% to 75%, and 1 patient appeared to have complete involvement of the femoral head. Among the displaced fractures, 30% (6/20) had a radiographically evident malreduction. Radiographs were adequate for evaluation of hardware placement in 78% (21/27) of the fractures. Central placement of the hardware was noted in only 9% (2/21). Superolateral positioning of the hardware within the femoral head was most frequently noted.