This study examined the cardiovascular responses of 22 healthy subjects (mean age 48 years) to two methods of weighing--over bed and standing scale. Variables were measured at one-minute intervals during the weighing treatments and a rest period after each treatment and included: cardiac output, stroke volume, heart rate, the ratio of pre-ejection period to left ventricular ejection time (a measure of contractility), blood pressure, mean arterial pressure and total peripheral resistance. Mean changes during the weighing treatments demonstrated activation of reflex responses to gravitational shifts in blood volume, which were opposite in direction between the two methods and attributed to posturally-induced shifts in venous return. During the five-minute rest period after weighing, all values rapidly returned to baseline. Compared to baseline measures, responses during the weighing treatments differed significantly between treatments (p less than 0.01), but none differed significantly between rest periods.