BACKGROUND The impact of transfusion of aged red blood cells (RBCs) on the outcome after coronary artery bypass grafting (CABG) is controversial. This issue has been investigated in the present study. MATERIALS AND METHODS Data on perioperative blood transfusion, storage time of RBCs, and adverse events were available for 819 consecutive patients who underwent isolated CABG and received two to four units of RBCs. The maximum RBC storage time was 35 d. RESULTS Repeated-measure test showed that transfusion of all RBC units >14 d and at least one RBC unit >14 d was associated with similar postoperative C-reactive protein (P = 0.245 and P = 0.103, respectively) or creatinine levels (P = 0.414 and P = 0.259, respectively) compared with newer RBC units. Propensity score-adjusted analysis showed similar immediate and late outcome in patients receiving only newer RBCs compared with those who received only older RBCs. Similar findings were observed in patients receiving only newer RBCs compared with patients who received at least one unit of older RBCs. Logistic and proportional hazards analyses adjusted for the number of RBC units showed that the median storage duration of RBCs was not associated with either any of the immediate outcome end points or late mortality. CONCLUSIONS These findings suggest that, when the maximum RBC storage time is 35 d, the duration of storage of transfused RBCs does not affect the immediate and late outcome of patients with moderate bleeding after CABG.