Aim of the present study was to assess, in a pair-matched analysis design, risk factors for post-transplant diabetes mellitus (PTDM) in renal transplant recipients (KTx). The incidence of PTDM was evaluated in 538 consecutive KTx in relation to their baseline immunosuppression. PTDM was defined according to the 2003 American Diabetes Association and World Health Organization experts committee definition. As risk factors for PTDM development were considered: age, family history of diabetes, body mass index (BMI), baseline immunosuppression, doses and blood levels of the immunosuppressive agents used. Baseline immunosuppression consisted of CSA, TAC and SRL + CNI. Thirty-two pair-matched controls were identified among the 538 KTx and included in the risk analysis. Significant risk factors for the development of PTDM were identified in the family history of diabetes (P < 0.02) and BMI (P < 0.05). Higher BMI and positive family history for diabetes mellitus were significant risk factors for the development of PTDM, regardless of the immunosuppressive agent used.