Background. Pancreatitis following cardiopulmonary bypass is a well-known complication in adults undergoing cardiac surgery. However, the occurrence of pancreatitis in pediatric patients undergoing repair of congenital heart disease is under-appreciated. Post-Fontan patients are particularly prone to postoperative pancreatitis. In an effort to identify specific perioperative factors predictive of postoperative pancreatitis, we retrospectively reviewed a group of Fontan patients. Methods. From June 1996 to June 2001, 40 patients underwent a modified Fontan operation. Four patients developed acute pancreatitis postoperatively. The preoperative, intraoperative, and postoperative hemodynamics and ventricular function parameters were retrospectively analyzed and compared to 10 randomly selected Fontan patients who did not have pancreatitis. Preoperative echocardiographic and angiographic data, including digitized ventricular pressure tracings, were reviewed to obtain ventricular relaxation time constant (tau), pulmonary vascular resistance (PVR), ventricular end diastolic pressure (VEDP), positive dp/dt and negative dp/dt values. Results. Patients developing acute pancreatitis had very high mortality (50%) compared to no mortality in the control group. The mean preoperative tau was significantly prolonged (41 ms vs 26 ms in control group, p < 0.001), and pre operative systemic output (Qs) lower in the pancreatitis group (mean 2.75 L/min/m2) compared with controls (Qs of 5.09 L/min/m2, p < 0.03). Conclusions. Impaired ventricular relaxation and decreased preoperative cardiac output are predictive of increased risk of postoperative pancreatitis in Fontan patients. Evaluation of preoperative diastolic function in these patients may provide additional insights in to clinical outcome following the Fontan procedure.