Brachial artery pressures determined by the oscillometric method were compared with simultaneous central aortic (Ao) pressure measurements in 30 patients undergoing cardiac catheterization. Three simultaneous oscillometric and central Ao pressure readings were obtained in each patient. Central Ao pressures ranged widely for systolic (SP) (98 to 177 mm Hg), diastolic (DP) (41 to 97 mm Hg), and mean (MP) (60 to 120 mm Hg) pressure values. The mean percent errors (pressure difference divided by central Ao pressure) and "within subject" standard deviation were 1% and 3% for SP, 2% and 4% for DP, and -3% and 7% for MP. The percent error in oscillometric SP and DP estimates was not significantly influenced by cardiac index, systemic vascular resistance, heart rate, body surface area, or left ventricular ejection fraction. The oscillometric method provides accurate, reproducible, and convenient estimates of central Ao SP and DP and may be particularly useful when indirect blood pressure measurements are required for the noninvasive assessment of left ventricular function in patients without aortic stenosis.