R80122 (0.3 mg/kg body weight), a new phosphodiesterase inhibitor, was tested in ten patients undergoing coronary artery bypass surgery. Haemodynamic measurements were made and hepatic blood flow assessed by the indocyanine green infusion method using liver vein catheterization. Cardiac index increased by 63% and systemic vascular resistance decreased by 47%. Hepatic blood flow and intestinal vascular resistance were not significantly affected; nor was hepatic oxygen consumption. It is concluded that R80122 is a highly cardioselective phosphodiesterase inhibitor and that the reduction in systemic vascular resistance by this drug is not an effect of extensive intestinal vasodilatation.