Seventeen patients with arthrosis secondary to congenital dislocation or dysplasia of the hip were treated by total hip replacement. Nine hips were completely dislocated, while 12 were dysplastic and subluxated. The operation was performed as a modification of Charnley's standard technique, the acetabular prosthesis was always placed in the neoacetabulum, and no particular attempt was made to correct the shortening of the leg. In eight patients bone grafting to the upper lateral acetabular edge was done. Only a few complications occurred and no postoperative dislocations. On average 4 years after the operation, the clinical and radiographic results were satisfactory. The operation used here is less difficult than placing the cup in the original acetabulum.