BACKGROUND: Systemic arterial hypotension is relatively common following initiation of cardiopulmonary bypass (CPB). Decreased blood viscosity is induced by acute normovolemic hemodilution (ANH) and by the use of crystalloid oxygenator prime. The purpose of this paper is to study the effect of ANH on mean arterial pressure, perfusion flow index and PaO2/FiO2 upon initiation of CPB, and on homologous blood usage during CPB in coronary artery bypass grafting (CABG) surgery. METHODS: We reviewed 30 patients constituting an ANH group, and 30 patients in a control group who had undergone CABG surgery within the past 2 years. In the ANH group, 1 or 2 units of fresh autologous whole blood were sequestrated following induction of anesthesia. We compared mean arterial pressure, perfusion flow index, PaO2/FiO2, and hematocrit on the initiation of CPB, and homologous blood usage during and post CPB periods between the groups. RESULTS: Upon initiation of CPB, hematocrit in the ANH group was significantly less than in the control group, but there was no significant difference in mean arterial pressure, perfusion flow index or PaO2/FiO2 between the groups. The use of homologous blood during CPB in the ANH group was not significantly higher than in the control group. CONCLUSIONS: Acute intraoperative normovolemic hemodilution in CABG surgery was safely performed without significant hypotension and increased homologous blood usage during CPB.