Mycophenolate mofetil (MMF), an immunosuppressant that is widely used in renal transplant, is associated with several dose-dependent hematologic and gastrointestinal side effects that lead to dose reduction or even discontinuation. The aim of this study was to compare the renal allograft function and acute rejection episodes in kidney allograft recipients who were on two different doses of mycophenolate mofetil for at least five years. Fifty-five kidney allograft recipients who were on MMF were randomly selected and followed for evidences of acute rejection or drug side effects. All patients were followed for at least five years after transplantation. Renal function tests (blood urea and serum creatinine) were measured monthly for two years and then every two months Twenty-two patients (40%) underwent MMF dose reduction to 1.35-0.23 gr/day due to perceived side effects or economic reasons (group 1). The mean time for this change was 4.2 - 2.1 months after the kidney transplant. The remaining patients (group 2, n =33) were continued on MMF 2 g/d drug dosage. Statistical analysis was performed using SPSS 11.0 (Student t test). A P value <0.05 was considered significant. Results. The two groups were comparable regarding age, gender and their immunosuppressive medications. The renal function tests were comparable between the two groups at the end of this study. Mean blood urea were 44.8 +/- 5.8 and 46.8 +/- 6.8 mg/dl in group 1 and 2, respectively (P > 0.05). Mean serum creatinine were also 1.32 +/-0.14 and 1.38 +/- 0.21 in group 1 and 2, respectively (P > 0.05).There were two graft losses and one patients loss in group 2. There was also 2 graft loss among group 1 patients. In conclusion, our study showed that MMF dose reduction is not associated with an increased risk of acute renal allograft rejection or impaired allograft function in a five-year follow-up period.