Subtrochanteric fracture of the femur has been infrequently reported after in situ fixation of slipped capital femoral epiphysis, and this occurred in only 1.4% of our patients over a 10-year period. As this technique is used more frequently, however, the incidence of this complication is likely to rise. All four subtrochanteric fractures occurred through unused drill holes, and avoiding extraneous screw holes seems to be the best way to prevent postoperative subtrochanteric fracture. Once subtrochanteric fracture occurs, immediate open reduction and internal fixation with a compression hip screw device is the recommended treatment.