Eight young men were twice administered--on two different days--a series of hemodynamic (using an impedance plethysmograph), subjective, and skin temperature measurements during 5 h of quite sitting. On one day, a Circutone seat (massage-type seat cushion) was activated for 14 min/h, and on the other day it was not. During the "Circutone off" day, 5 h of sitting resulted in a continuous decrease in calf blood flow and an increase in venous blood pooling in the calf; an increase in blood pressure and a stable cardiac output (4.6 l/min); very low urine output; large increases in skin temperatures at the body areas in contact with the seat (thigh and lower back); and increases in various subjective responses of discomfort. The Curcutone activation resulted in a substantial exchange of the stagnant blood in the calf and thigh; a tendency to increase thigh and calf blood flow; a decrease in venous pooling in the thigh; and less subjective discomfort. The Circutone activation had no effect on skin temperature. The results indicate that the Circutone seat improved seat comfort by improving local circulation, especially in the thigh, which probably accounted for the improved subjective reactions.