Fifty patients who underwent total hip replacement were examined within 3 months by two independent investigators with respect to functional impairment of the sacroiliac joint. Several well-defined clinical tests were used, e.g. spine test, standing flexion test, Menell's sign, tenderness of the sacroiliac joint. The results of both investigators were comparable, with corresponding results in 94 per cent. Nearly 30 per cent of the patients showed functional impairment of one sacroiliac joint. This finding may partly cause the gluteal or low back pains which are reported by patients after hip replacement.