Objective: Normothermic perfusion has been proposed as a more physiologic technique than hypothermic perfusion during cardiac operations. The aim of this study was to evaluate the effects of systemic perfusion temperature on clinical outcome in patients undergoing mitral valve replacement. Methods: Fifty patients with similar clinical and operative data were prospectively randomized into two groups: hypothermia (rectal temperature 28-30°C group A, n=25), and normothermia (rectal temperature 35-37°C group B, n=25). In both groups cold crystalloid cardioplegic solution and topical hypothermia were used. Results: During cardiopulmonary bypass (CPB) systemic vascular resistance (SVR) was significantly lower in group B patients (P