The present investigation compares the systemic and regional haemodynamics in nicorandil-treated and solvent-treated pigs with a concentric stenosis around the left anterior descending coronary artery. The stenosis per se led to a decrease in mean arterial blood pressure, cardiac output, stroke volume, maximum rate of rise in left ventricular pressure and transmural (more marked in the endocardium than in the epicardium) blood flow to and myocardial wall motion in the post-stenotic segment. Infusions of nicorandil (15 and 30 micrograms.kg-1.min-1, intravenously) decreased arterial blood pressure, cardiac output and the maximum rate of rise in left ventricular blood pressure. There was a tendency for epicardial blood flow in the non-stenotic segment to increase but blood flow to the ischaemic myocardium (epicardium as well as endocardium) was further compromised. Using the postsystolic wall thickening as an index for the viability of the myocardium and the Bretschneider formula for myocardial oxygen demand and the calculated myocardial oxygen consumption, we found that nicorandil further compromised the oxygen balance but did not jeopardize the viability of the myocardium. Regionally, nicorandil decreased renal blood flows but enhanced blood flows to the brains and adrenals. It is concluded that nicorandil lacks beneficial effects on the ischaemic myocardium in pigs with a concentric coronary artery stenosis. Apparently, the potential adverse effect (decrease in coronary perfusion pressure) of nicorandil outweighs its potential salutary effects (coronary vasodilatation and decrease in myocardial oxygen consumption due to peripheral vasodilatation.