Restoration of retroacetabular bone stock by curettage and grafting with synthetics would obviate the need for autograft or allograft bone and prevent bone loss associated with revision. We conducted a clinical and radiographic review of 7 patients with progressive retroacetabular osteolysis. The size of the lesions ranged from 3.1 x 2.0 to 9.0 x 5.3 cm(2). All patients were treated with curettage and filling of the defects with calcium sulfate. Mean follow-up time was 48 months. On follow-up evaluation, there was resolution of 4 lesions, good osseous integration of 2 lesions, and no progression of 1 lesion. Curettage and grafting of progressive retroacetabular osteolysis with calcium sulfate and retention of components result in good osseous integration of the graft and halt the progression of lysis.