Aortic root pressure and flow data can be used to assess left ventricular (LV) performance and properties of the systemic arterial tree. The calibrated subclavian arterial pulse trace was combined with echocardiographic imaging and Doppler velocity recordings to obtain noninvasive estimates of aortic root pressure and flow in 8 healthy subjects (group A), 12 patients with recent myocardial infarction (group B), and 8 with healed myocardial infarction and a dilated left ventricle (group C). The pressure and flow data were transferred to a computer and processed in specially designed software, including a new procedure for estimation of 3-element windkessel model parameters. There were no significant group differences for either aortic root pressure estimates or heart rate. In groups B and C, stroke and cardiac indexes were lower and total peripheral resistance higher than in group A. There were no group differences in the model estimates of total arterial compliance, whereas the characteristic impedance was greater in group C than in A, indicating a less compliant aorta in C. Both LV total and steady power were less in groups B and C than in A, whereas no group difference was found for percent oscillatory power. The reproducibility for recording was good for the aortic root pressure estimates, and lower for the derived parameters (stroke and cardiac indexes, windkessel model parameters and LV power), whereas that for interpretation was generally good. This method provides a unique noninvasive access to important parameters of LV function and the systemic circulation.