Kidney transplantation is now considered to be the treatment of choice for patients with end-stage renal disease (ESRD). Post-transplant diabetes mellitus (PTDM) is a well recognized complication of renal transplant. PTDM is reported to be contributory to major infections and cardiovascular complications leading to increased post-transplant morbidity. The present study was conducted to evaluate the frequency of PTDM in our center to identify the role of immunosuppressive therapy and other risk factors in the genesis of PTDM and also to assess the impact of PTDM on graft and patient survival. Since Nov. 1998 till Nov. 2003, 1000 renal transplant recipients were followed in Shiraz (Southern Iran) Organ Transplant Center, including 369 cases with pre-transplant DM, and 631 non-diabetic cases, of whom 131 developed Post-transplant diabetes. PTDM was defined as with the WHO criteria for purpose of this study. Information on age, sex, blood group, underlying cause of ESRD, donor type, type of immunosuppressive therapy and serum creatinine level were collected by a retrospective review of hospital records; the data were analyzed using SPSS software. PTDM occurred in patients with mean age of 34.7±7.4; M/F ratio was 1.8. The most common blood group was A, and the most common cause of ESRD was unknown. 23 PTDM patients (21%) underwent cadaveric renal transplant. Mean serum creatinine at the time of diagnosis of PTDM was 2.1±0.5 mg/dl. Graft loss and mortality was significantly higher in PTDM vs. non-diabetic group. The overall reported incidence of PTDM worldwide varies from 3.4% to 46%; such incidence is 22% in our center; high incidence of obesity and genetic background may have led to such a high figure. Higher age was associated with higher risk of acquiring PTDM in our center as in other middle eastern reports. We also found a significantly higher incidence of PTDM in living related cases (p<0.05).