Arterial pressure was considerably higher than the cuff pressure obtained by auscultation or palpation of the brachial artery in 18 patients with shock and high total peripheral vascular resistance. Pulse pressure was also greatly underestimated by indirect measurement. This discrepancy was not observed in 21 hypotensive patients with low or normal resistance. Infusion of vasoconstrictor drugs into the arm circulation of normal subjects reproduced the clinical situation of normal arterial pressure with absent Korotkoff sounds and diminished radial pulses. High vascular resistance in the upper extremity prevents the hemodynamic events which normally produce the Korotkoff sounds. Disappearance of peripheral pulses is probably the result of reduced stroke volume and increased arterial wall stiffness.