The effect of nisoldipine on the vasoconstrictor effect of histamine on coronary vascular resistance, cardiac performance and myocardial oxygen consumption was determined in this study. In a supported working heart preparation a perfluorochemical emulsion (FC-43) was used a perfusate. To enhance the sensitivity of the large coronary arteries to vasoconstrictor stimuli, the endothelium was removed mechanically from the large coronary arteries. The changes in coronary artery diameter were documented by colour arteriography. Nisoldipine reduced the constriction of coronary arteries and the decrease in coronary flow induced by histamine. Nisoldipine abolished or reduced the decrease in cardiac output, left ventricular end systolic pressure, dP/dt and myocardial oxygen consumption. In the supported working heart preparation, nisoldipine is an effective dilator of large coronary arteries deprived of endothelial lining.