Conservative treatment of slipped epiphysis has now been superseded by surgical procedures. If the slipping is slight or moderate, bone-pegging or fixation in situ with a nail is indicated. In our series of 185 nailed hips, the complications which occurred in the patients operated upon were: driving away of the epiphysis, bending of the guide wire, perforation of the cortex of the femoral head, gliding of the nail, femoral fracture, and necrosis of the femoral head. Only in one patient had complicating necrosis of the femoral head any permanent effect on the hip. The frequency of complications was lower following the use of blunt three-flanged nails. Wedge osteotomy of the femoral neck performed on patients in the series of eighty-four hips was followed by necrosis in 27 per cent and it is questionable whether this method is justified.