This study was undertaken to determine the incidence and clinical features of avascular necrosis of bone in 69 transplant recipients all of whom had a functioning allograft for at least 12 months. An attempt was also made to identify any potential predisposing factors. The patients were assessed by an orthopaedic surgeon. The diagnosis of avascular necrosis was made on the basis of radiographs and isotope bone scans. Fourteen patients (20.2%) developed avascular necrosis with a mean onset of 19 months post-transplantation. The hip joint was most commonly affected. The isotope bone scan was the most sensitive diagnostic tool; abnormalities were detected before the onset of symptoms in 4 patients. Avascular necrosis was more common in Indian transplant recipients and was also associated with: (i) cadaver transplants; (ii) more frequent bouts of acute rejection (P < 0.05); and (iii) a greater incidence of other steroid-associated side-effects (P < 0.05). Alcohol consumption and radiological evidence of osteoporosis were more prevalent in the avascular necrosis group (42.8% v. 29.0% and 28.5% v. 7.2% respectively). Avascular necrosis did not correlate with age, sex, renal function at 1 year or severe secondary hyperparathyroidism. This study suggests that corticosteroid therapy plays an important role in the pathogenesis of avascular necrosis. Excessive alcohol consumption and osteoporosis also appear to be risk factors.