Six patients with recurrent dislocation after total hip replacement have been treated by fixing an additional sector to the acetabular component. Muscle imbalance or unsatisfactory positioning of the prosthetic components (or both) had caused the dislocations in five patients. In the sixth, a schizophrenic, the dislocations were due to the positions in which the patient placed his limb. At operation a sector was cut from another acetabular prosthesis and screwed on to the previously inserted acetabular component in such a position as to prevent further dislocation. This method has been successful and seems a simple alternative to exchange arthroplasty.