This study was designed to measure certain cardiovascular effects of 2 or 11 micrograms nifedipine/kg body weight given intravenously to dogs anesthetized with fentanyl-droperidol-pentobarbital. Parameters measured were: cardiac output, stroke volume, stroke work, systemic arterial pressure and vascular resistance, splenic weight (a measure of venous capacitance), and fractionation of cardiac output to many tissues. In response to doses of nifedipine, systemic vascular resistance decreased, cardiac output and flows to most organs increased, and heart rate, stroke work, and splenic capacitance were unchanged. The flow to the diaphragm increased more than that to other organs.