Effects of furyl-dihydropyridine I (FDP-1) on collateral circulation were observed in ischemic myocardium of dogs. FDP-1 (200 mu g.kg(-1)) of intracoronary injection increased collateral flow, reduced systemic artery resistance, and coronary systolic pressure in infarcted region and the area of infarction decreased from 28.9+/-1.3 % to 15.3+/-1.2 % (p<0.01, n=6). The results indicated that FDP-1 could improve coronary collateral circulation, increase collateral flow in ischemic region, decrease myocardial oxygen demand, and protect myocardial ischemia.