Total hip replacement has been very successful in patients with painful, stiff hips associated with protrusio acetabuli, but the heat of polymerisation of methylmethacrylate cement may cause necrosis of the thin medial wall with consequent danger of migration of the cup. Since 1968 at Wrightington, thin slices of the head of the femur have been used as bone grafts to reinforce the acetabulum. We have reviewed 61 hips in 51 patients at an average of 4 years 3 months after operation. Grading for severity is discussed and the degree of physiological remodelling of the medial wall of the acetabulum after grafting assessed. There was an average of about 4 mm of remodelling, but this varied considerably; most took place within the first year. In no case was there relapse of the protrusio.