Avascular osteonecrosis (AVN) is a serious osseous complication after renal transplantation. Its prevalence clearly decreased from 20% to 4% after introduction of cyclosporine and reduction of steroid doses. The aim of our study was to evaluate the frequency of AVN among kidney transplant recipients and to determine the risk factors by comparing them with a population without AVN. Among 326 kidney transplant recipients between June 1986 and December 2004, 15 patients developed AVN with mean age of 40.86 years, including 11 men and 4 women. Fifteen kidney transplant recipients without AVN were selected to be matched for age, gender, and date of transplantation (control group). Cases of symptomatic AVN were diagnosed by hip X-ray, radioisotope bone scan, or magnetic resonance imaging. AVN was diagnosed at a mean of 3.5 years after transplantation (range, 0.5-13 years). The main localization of AVN was the femoral head in 12 cases and the femoral condyle in 3 cases. We studied the following risk factors: the type of donor (cadaver or living donor), the duration on dialysis before transplantation, the cumulative steroid dose, the acute rejection rate, and the posttransplantation weight gain. Statistical analysis showed that the cumulative steroid dose and the acute rejection rate were higher among the AVN group than the control group (P=.04 and P=.058, respectively). The prevalence of AVN in our population is 4.6%, which is probably an underestimate since these were symptomatic cases. The reduction or early withdrawal of steroids remains the only efficient preventive treatment for AVN.