We analyzed retrospectively the relationship between coagulation profile, and either hepatic function or hemodynamics, in patients who had undergone a Fontan-type procedure, comparing them, first, with a control group of 12 patients without significant hemodynamic abnormality, and, second, with a group of 14 patients who had not undergone a Fontan procedure, but whose mean right atrial pressure exceeded 8 mmHg. Follow-up catheterization had been performed in all 30 patients submitted to the Fontan-type operation. Prothrombin time, and factor XIII, were significantly lower in those who had undergone the Fontan procedure than in the other groups. Those submitted to the Fontan operation also had lower levels of protein C than controls, and their levels of plasminogen were lower than the patients with high right atrial pressure. Both aspartate aminotransferase and alanine aminotransferase were higher in those undergoing the Fontan procedure than in the other groups, while gamma-glutamyltranspeptidase in these patients was higher than in the control group. Mean right atrial pressure was highest in those under-going the Fontan procedure, while cardiac index was lowest. Prothrombin time was correlated to some extent with aspartate aminotransferase, mean right atrial pressure, and cardiac index. Protein C correlated with both aspartate aminotransferase and mean right atrial pressure, while factor XIII correlated with alanine aminotransferase, mean right atrial pressure, and cardiac index. Aspartate aminotransferase, alanine aminotransferase, and gamma-glutamyltranspeptidase, parameters of hepatic function, correlated significantly with mean right atrial pressure. In those who had undergone the Fontan procedure, decreased synthesis of pro-and anti-coagulant factors is a risk factor for both thrombosis and bleeding. Abnormal hemodynamics, in the absence of a right sided pumping chamber, may predispose to subclinical hepatic dysfunction, leading to selective disturbances of protein synthesis.