Adults who have osteoarthritis that is secondary to mild congenital dysplasia can be treated with total hip replacement using customary techniques. Those who have severe acetabular dysplasia or total congenital dislocation usually require augmentation of acetabular bone stock in order to carry out the total hip replacement. We reviewed the results of forty-seven total hip replacements in thirty-eight patients (age range, sixteen to sixty-eight years; average age, forty-seven years) who required autogenous grafting with bone from the femoral head for severe acetabular deficiency. The average length of follow-up was 7.1 years (minimum, five years). All grafts united. The average preoperative Harris hip rating was 46 points and the average postoperative rating was 74 points. Five hips (approximately 10 per cent) had a failure that required reoperation; four hipshad aseptic loosening of the acetabular component and in the fifth sepsis developed after a reoperation to reattach the greater trochanter. For the remaining forty-two hips, the average postoperative Harris hip rating was 78 points. Six additional sockets (approximately 15 per cent) were definitely loose by radiographic criteria, making a total of ten hips (approximately 20 per cent) with definite aseptic loosening of the acetabular component. The major factors that contributed to this aseptic loosening were complexity of the surgical procedure, necessity for a graft, lack of a small-sized metal-backed acetabular component, young age, obesity, lack of posterior support, and resorption of the graft. Dislocation was common, occurring in five (approximately 10 per cent) of the hips.(ABSTRACT TRUNCATED AT 250 WORDS)