Since November 1999 we have attempted to use a right heart bypass (RHB) system for beating heart coronary artery bypass grafting (CABG), which system produce better exposure of lateral and posterior wall of the heart and so enable us to facilitate bypass grafting to these branches. We report on our initial clinical experience with this system and the purpose of this study is to evaluate the efficacy of this system. To clarify the efficacy of the RHB system, we compared the intraoperative and postoperative clinical course, as well as outcome, between patients who underwent beating heart CABG with RHB and patients without RHB. Seventy-seven patients underwent beating heart CABG with RHB (RHB group) between November 1999 and December 2001. In the same period, 88 patients underwent beating heart CABG without RHB. Of these latter, 30 patients needed displacement of the beating heart in order to expose target coronary arteries (OPCAB group). Perioperative clinical parameters were compared between the groups. Patients in the RHB group received more grafts (2.4±0.6) than patients in the OPCAB group (2.0±0.2, p=0.002). There were no hospital deaths in either group. While displacing the beating heart, SvO₂ decreased and pulmonary artery pressure increased in both groups. Nevertheless, the value of SvO₂ was significantly higher in RHB group while displacing to expose the circumflex region (p=0.048) and the distal right coronary artery region (p<0.01). The effect of elevation of pulmonary artery pressure in the RHB group was lower than that in the OPCAB group, but it was not statistically different. Water balance during operation was 2, 898±1, 019ml in the RHB group and the 2, 237±807ml in OPCAB group (p=0.002). Body temperature following operation was 36.0±0.8°C in the RHB group and 36.5±0.8°C in the OPCAB group (p<0.01). However, no differences were found in postoperative blood loss, required transfusion, duration of mechanical ventilation, ICU stay and hospital stay. No patient had postoperative complications related to the RHB system. The introduction of the RHB enabled bypass grafting to posterior wall vessels with better exposure and under greater hemodynamic stability. Therefore we think it a very effective support system which enable multiple coronary revascularization on beating heart CABG.