Background: There are some paradoxical results about complications of long time stored blood transfusion. In this research we surveyed these clinical complications and relationship between morbidity and mortality with time of storage.Methods: This cross-sectional study was performed on 100 coronary artery bypass graft (CABG) candidates in Chamran Hospital, Iran, in 2010. We compared the complications of using old blood (with storage time more than 14 days) and fresh blood (with storage time less than 14 days). Renal complications were assessed by blood urea nitrogen (BUN) and creatine (Cr) levels. In addition, liver complications were evaluated based on prothrombin time (PT) and partial thromboplastic time (PTT).We also measured ICU stay, ventilation time and mortality in the two groups.Findings: Renal complications, bleeding after surgery, raised coagulation test values such as PTT were significantly more prevalent in old blood takers (P=0.001, 0.003, and 0.007, respectively).However, there were no significant differences in hemoglobin (P=0.001), hematocrit (P=0.001), platelet count (P=0.001) and mortality between the two groups.Conclusion: In accordance with previous research, the results of this study showed blood storage more than 14 days to increase complications after surgery. Therefore, fresh blood transfusion is recommended for CABG patients.