Numerous clinical studies demonstrated that mycophenolate mofetil (MMF) was significantly more effective in prevention of acute rejection episodes than azathioprine. Since the data supporting the long-term benefits of MMF therapy are not available, and considering the high cost of this therapy, we examined the safety of conversion from MMF to azathioprine in renal transplant patients. In 12 renal transplant patients (4 cadaveric and 8 living related donors) on triple immunosuppressive therapy (prednisone/MMF/cyclosporine) conversion from MMF to azathioprine was done after the first six to twelve post-transplant months. The majority of patients were in the low immunological risk of transplantation, and 7 (58.3%) received antithymocite globulin due to the delayed graft function. The mean follow-up period after the conversion to azathioprine was 6.4 months (range 3-12 months). Acute rejection episode was noticed only in one patient 8 months after the conversion following acute graft pyelonephritis. In all other patients graft function remained unchanged. We have concluded that the conversion from MMF to azathioprine in renal transplant patients on triple immunosuppressive therapy is safe and without detrimental effects on short-term allograft function. Long-term follow-up studies on larger number of patients are needed to confirm these observations.