In 26 renal allograft recipients treated with low-dose steroids and cyclosporin A (CyA) the CyA was withdrawn after 3 months and azathioprine substituted. Seventeen patients (65%) had no rejection episodes after stopping CyA (mean follow-up of 13 months). Only 2 patients (7.7%) developed acute rejection episodes in the first month after withdrawal of CyA. In 1 the rejection was easily reversed with intravenous methylprednisolone but in the other CyA had to be reintroduced; graft function then improved. Despite the very low dose of CyA used, a comparison of the mean plasma levels of urea and creatinine in the month before and after stopping CyA revealed a significant fall (P less than 0.001). The findings suggest that this policy is safe and avoids the potential hazards of long-term CyA.