Renal perfusion has been shown to be preserved or improved during treatment by tertatolol in patients with arterial hypertension. The aims of the present study were (1) to document the central and renal hemodynamic effects of tertatolol in normal subjects and (2) to look for a possible interaction between tertatolol and products of the cyclooxygenase pathway of arachidonic acid metabolism. Five mg of tertatolol, 1 g aspirin, 5 mg tertatolol together with 1 g aspirin, and placebo were administered to 8 healthy volunteers at 1 week intervals in a random order and in a double-blind fashion. Cardiac output was measured by cardiac Doppler echography and renal blood flow and glomerular filtration rate by constant infusion techniques using I123-iodohippurate and Cr51-EDTA respectively. Measurements were performed before and then successively 2 and 4 h after oral intake of drugs or placebo. Tertatolol alone or with aspirin significantly decreased heart rate and cardiac output (P less than .05) without change in blood pressure, renal blood flow or glomerular filtration rate. The renal fraction of cardiac output was increased by tertatolol alone or with aspirin (P less than .05). Either placebo or aspirin alone had no effect. Thus tertatolol redistributes cardiac output to the kidneys in normal subjects as previously reported in hypertensive patients. This favorable effect on renal hemodynamics appers unlikely to be mediated by a local release of vasodilating prostaglandins.