Aortic and radial arterial pressure measurements were compared after cannulation and before cardiopulmonary bypass in 26 patients scheduled for coronary artery bypass grafting. The radial artery blood pressure range was 89 to 147 mm Hg systolic and 44 to 75 mm Hg diastolic. A difference was found between the central and peripheral dicrotic notch pressures, the former being 7.9 +/- 2.7 (SD) mm Hg higher than the latter. When 8 mm Hg was added to the notch pressure measured in the radial artery to construct a calculated end-systolic pressure, there was good agreement with the centrally measured notch pressure. The mean difference was -0.15 mm Hg with a 95% confidence interval of -1.2 to 0.9 mm Hg. It was not possible to calculate peak systolic aortic pressure with the same accuracy from the systolic and diastolic pressure measurements in the radial artery. It is concluded that left ventricular end-systolic pressure measured as the aortic dicrotic notch pressure can be calculated from the dicrotic notch pressure in the radial artery with reasonable accuracy.