In this study Hb concentration secondary to enalapril (E) and /or losartan (L) is evaluated with respect to renin-angiotensin system (RAS) polymorphisms. After determination of RAS polymorphisms consist of ACE (DD, non-DD), Angiotensinogen (TT, non-TT) and angiotensin receptor (CC, non-CC) by PCR, seventy renal transplant recipients were recruited to four groups randomly: first and second groups were treated with E (10mg/d, 15 patients) and L (50mg/d, 20 patients) alone respectively. Third group received E+L (10mg/d + 50 mg/d, 13 patients) and the forth group (22 patients) received no medication. The treatment protocol was followed for 16 weeks. Complete blood counts were checked before treatment and every 2 months. P<0.05 was considered to indicate statistical significance. Treatment for 4 months decreased the Hb level in the E+L (14.15±0.94 to 12.06±0.66 g/dl, P=0.000); E (14.00±0.86 to 13.11±0.82 g/dl, P=0.02) and L (14.12±0.90 to 12.10±2.35 g/dl, P=0.01) groups, but not in the control group (13.55±0.70 to 13.36±0.69 g/dl, P=0.22). None of the above regimens was more Hb reducer than the others (P=0.21). DD genotype of ACE was the only genotype among the RAS polymorphisms, which associated with higher Hb concentration (14.29±0.41 vs. 13.44±0.76, P=0.04). Any other sets of RAS polymorphisms (alone or together) did not impact on Hb levels in pre and post intervention. Our findings suggest that low dosage of ACEI and/or ARB in RTRs can decrease Hb levels regardless to the RAS polymorphisms.