The aim of this study was to investigate the effect of peritoneal dialysis (PD) on fluid balance and renal function in 17 infants with low cardiac output syndrome after open heart surgery. Peritoneal catheters were inserted prophylactically at the end of the cardiac operation. An effective negative fluid balance was achieved in all infants (P<0.01). They had significantly increased diuresis (P<0.01), increased mean arterial blood pressure (P<0.05), decreased central venous pressure (P<0.05), and decreased dopamine medication (P<0.05) after PD compared to before PD. Complications of PD, present in 7 patients, were transient and of minor significance. No patients died during PD or required discontinuation of PD due to severe cardiorespiratory distress. Thirteen patients recovered and had normal function upon discharge from our ward. Four died due to severe congestive heart failure. The overall mortality rate among all 17 patients was 24%. We conclude that PD is helpful in promoting fluid removal and may be used prophylactically for those infants who are at high risk for low cardiac output after cardiac surgery.