Eleven patients in a series of 400 cases of systemic lupus erythematosus developed a new complication of that disease, namely, avascular bone necrosis. The femoral head was involved bilaterally in eight patients and unilaterally in one. Two patients had bilateral damage to the femoral condyle. The average age of onset of bone symptoms was 36 years with a mean of 5.1 years after the appearance of the underlying disease. There was no relationship between corticosteroid therapy and the appearance of osseous pain. The disease process when once started was insidiously progressive in all cases but one, and led eventually, in 8 patients, to destruction of the joint with loss of mobility. Although therapy may yield symptomatic relief there was no radiographic evidence of improvement. The appearance of bilateral avascular necrosis should suggest systemic lupus erythematosus as a possible etiological factor.