We studied the effect of nicardipine on the canine cardiovascular system, especially on total blood volume and vascular compliance. Under light halothane anesthesia, nicardipine decreased total blood volume significantly (from 80.0 ± 8.4 ml/kg in the control state to 75.3 ± 8.0 ml/kg under nicardipine administration, p< 0.01), while it increased central circulating blood volume (from 17.1 ± 5.9 ml/kg to 25.5 ± 8.2 ml/kg, p<0.01), increased cardiac output and central venous pressure, and decreased mean arterial pressure (from 134.3 ± 16.2 mmHg to 93.9 ± 17.1 mmHg, p<0.01) and total peripheral resistance. Vascular compliance derived from fluid infusion experiments showed a significant decrease (from 8.9 ± 3.8 ml/ mmHg/kg to 5.5 ± 8.0 ml/mmHg/kg, p<0.01 ). In addition to the vasodilatory action of nicardipine on arteries, these findings also suggest that 1) nicardipine causes a fluid shift from the vascular to the interstitial fluid space as a result of increased capillary pressure, 2) it increases preload through blood redistribution from the peripheral to the central circulation, and 3) it decreases compliance of the vassels, perhaps due to an indirect splanchnic venoconstriction.