A superficial vein in the wrist of a normal subject was examined with a high-frequency (30 MHz) ultrasound system with an annular-array broadband transducer. Spontaneous echo contrast was observed without compression in a cephalic vein 2 to 3 mm in diameter in the wrist. This echo was enhanced 1 hour after the subject had eaten and was further enhanced when the central side of the vein was compressed. Spontaneous echo contrast seen in larger veins studied using transmission frequencies of about 10 MHz has often been considered analogous to erythrocyte aggregation (rouleau formation) seen in cardiovascular moya-moya echo or other thromboembolic conditions. This increased spontaneous echo contrast seen after the subject has eaten a meal appears to resemble the aggregation of erythrocytes produced by compressing larger veins. The 30-MHz transducer detected echoes from blood in veins much smaller than those in which it had been detected previously. These echoes may have resulted from factors including erythrocytes or smaller rouleaux, as well as larger rouleaux. This intravenous echo contrast in superficial veins may prove useful in the noninvasive study of the physiologic dynamics of erythrocyte aggregation.