The aim of this study was to investigate the incidence of osteonecrosis of the hip and knee among renal allograft recipients treated with cyclosporin- or tacrolimus-based immunosuppressive regimens and its predictors focusing on the first 8 weeks after transplantation. The subjects were 232 renal allograft recipients who had MRI for osteonecrosis of the hip and knee 3 months or longer after transplant. The following potential predictors of osteonecrosis were tested using univariate and multivariate logistic regression analyses: age, gender, body weight, body mass index, duration on dialysis before transplant, number of human leukocyte antigen mismatches, ABO mismatches, type of transplanted kidney, immunosuppressive regimen, cumulative steroid dose and steroid pulses, incidence of acute rejection, and delayed graft function, defined as requiring dialyses in the first week. Evidence of osteonecrosis was visible on the MRI of 11 recipients (4.7%, 95% confidence interval 2.4-8.3). Univariate and multivariate logistic regression analyses indicated that delayed graft function was the most important predictor of osteonecrosis. In conclusion, we found a lower incidence of osteonecrosis of the hip and knee in renal allograft recipients treated with cyclosporin or tacrolimus. In the patients treated with improved immunosuppressive regimens, delayed graft function was a significant early predictor of osteonecrosis.