The hemodynamic effects of diltiazem were investigated in 6 volunteers at rest, supine and erect, under psychologic stress and orthostatic conditions. Plasma concentrations were also estimated. Under all conditions diltiazem showed a vasodilating property that was more pronounced on the arterial resistance vessels than on the pulmonary vessels. The 1st plasma concentrations were detected 15 min after drug intake and the highest values were seen in the 3rd h.