We analyzed the preoperative and perioperative data on sixty-nine consecutive complex total hip replacements performed in fifty-seven patients using miniature or microminiature custom-made femoral components. The patients' average age was 45.7 years. The preoperative diagnosis was congenital dysplasia or dislocation of the hip in 72 per cent of the hips. Acetabular bone grafts were required in thirty-seven of the sixty-nine hips. Operative complications occurred in thirteen (19 per cent) and postoperative dislocation occurred in eleven (16 per cent) of the sixty-nine hips. Fifty-five hips in forty-seven patients were followed for a minimum of two years, the average follow-up being 4.8 years and the longest, 9.8 years. All acetabular grafts united. Loosening of one or both prosthetic components occurred in ten (18 per cent) of the fifty-five hips (twelve of the 110 components became loose). There were no instances of a stem bending or fracturing, despite the small size of the femoral components. Eight hips (14.5 per cent) had undergone revision, six for painful loose components and two for recurrent dislocation. For the forty-seven hips that were not revised, the average Harris hip score rose from 43 points preoperatively to 80 points postoperatively.