The Presence of donor leukocytes in recipients of organ allografts has been shown even several years after transplantation. However, it remains unclear whether this donor cell microchimerism plays an effective role in allograft acceptance or is simply a consequence of immunosuppression condition in recipients. In this study we retrospectively evaluated the Peripheral Blood Microchimerism (PBM) after renal transplantation in 32 male-to-female recipients of living (unrelated) and cadaveric donor renal transplants. Using a nested Polymerase Chain Reaction (nested–PCR) amplification specific for SRY region of the Y chromosome microchimerism was detected with sensitivity up to 1:1000000. According to the presence of PBM recipients were classified into microchimeric and nonmicrochimeric groups, and then acute and chronic rejection episodes, type of allotransplant (living or cadaveric donor), recipient and donor age at transplantation, previous male labor or blood transfusion, allograft function (serum creatinine level), post-transplant period duration, and body mass index were compared between two groups. Among 32 recipients 7 were positive for PBM in multiple testing at different post-transplantation times. All microchimeric recipients had been received kidney from living-unrelated donors. The mean age of microchimeric group was 36.3±10 year vs. 36.3±11.9 year in non-microchimeric group, the mean transplantation duration was 73±29 month vs. 48±23 month (P-value<0.02), the mean serum creatinine level was similar in both groups1.07±0.4 mg/dl vs. 1.07±0.38 mg/dl, BMI was 24±5 kg/m2 vs.23±3.8 kg/m2, 5(71%) of microchimeric patients had history of blood transfusion vs. 19(76%) patients among non-microchimeric group, the history of male labor was 6(85%) vs. 12(48%) P-value>0.05 respectively. Regarding to all parameters mentioned above significant difference was not observed. In addition, acute rejection rate in microchimeric group was 3 (42%) versus 4 (16%) in nonmicrochimeric recipients (not significant). Our results demonstrate better establishment of microchimerism after living donor kidney transplantation. But, concerning true effect of microchimerism after renal transplantation doubt still persists; and it seems that microchimerism alone has no major protective role in renal allograft survival.