Project IB examined the effects of acute sodium loading and depletion on cardiovascular and hormonal reactivity as a function of race and sex. Normotensive subjects were classified according to two categories: Black or white race; male or female sex, with four cells of 15 subjects each. After the initial medical examination, subjects were seen three times at intervals of two weeks. Before each visit three overnight urine collections were made for electrolyte excretion evaluation. On these three visits subjects were randomized to either a control day, a sodium loading day, or sodium depletion day. On each of these days subjects were given three reactivity tests including the video game, exercise test, and speech-stressor task. The same psychological tests as in Project 1A were given on the mornings of the three testing days.