Tuberculosis (TB) is a common and serious problem after renal transplantation especially in developing countries. Conflicting results exist in concern to predisposing factors, such as pre transplantation tuberculin skin test (prePPD) positivity, pre transplantation dialysis time, and age, sex and allograft dysfunction. To describe correlation between these factors and post transplant TB, we evaluated this issue in our center.41 TB occurred among 1179 renal transplant recipients (3.48%) in our center, 79.31% pulmonary TB, and 23.69% extra pulmonary, with mortality rate 28.94%. among 41 patients (pts) 45.9% were female and 54.1% male, mean of age was 43.24 year, mean of pre transplantation dialysis time was 23.16 months. To evaluate predictive value for mentioned risk factors, we compare 21 TB infected pts after transplantation (G1), with 50 patients without TB involvement after transplantation (G2). Two groups were matched in respect to immunosuppressive protocols (cyclosporine, prednisolone, and azathioprine. Mean of age was 44.57 y and 41.34 y in G1 and G2 respectively. 10 pts (47.61%) in G1 were male and 11 pts (52.39%) were female in G2. mean of pre transplantation dialysis time was 24.11 m in G1 and 22.63 m in G2. 15 pts (71.43%) were prePPD negative and 6 pts (28.57%) were prePPD positive in G1. 29 pts (44%) were prePPD negative, and 21pts (56%) were prePPD positive in G2. All pts with positive prePPD had been received pre transplantation isoniazid prophylaxis. Mean of serum creatinine was 2.16 in G1 and 1.16 in G2. Thus PPD test has positive predictive value 22%, negative predictive value 66%, sensitivity 29%, and specificity 58%, in post transplantation TB. There was no statistical significant difference between G1 and G2 in respect to PPD positivity (p=0.294), age (p=0.356), sex (p=0.422), and pre transplantation dialysis duration (p = 0398), but there was significant difference between G1 and G2 in respect to mean of creatinine (p <0.003). We conclude that prePPD positivity with isoniazid prophylaxis, age, sex, and pre transplantation dialysis duration do not increase risk of post transplantation TB, but allograft dysfunction increases risk of TB significantly.