The pharmacological effects of benzopyran potassium channel openers (lemakalim, KR-30450 and KR-30818) on the occlusion/reperfusion-induced myocardial infarction were investigat ed. In anesthetized rats, subjected to 45-min occlusion of the left anterior descending coronary artery (LAD) followed by 90-min reperfusion, the infarct size was measured by calculating the ratio of infarct zone to area at risk (IZ/AAR) with the Evans blue/TTC technique. Rats were intravenously given vehicle (1% DMSO), lemakalim, KR-30450, and KR-30818 alone or in combination with a selective K$_{ATP}$ blacker glibenclamide, 30 min prior to coronary occlusion. Compared to vehicle, lemakalim (30 ${mu}$g/kg i.v.), the active enantiomer of cromakalim, had a tendancy to decrease infarct size. KR-30450(30 ${mu}$g/kg, i.v.). the newly synthetized potassium channel openers (PCOs), caused a reduction of infarct size (from 70${pm}$4%to 57${pm}$5%). but KR-30818 (30 ${mu}$g/kg, i.v.), a metabolite of KR-30450. did not modify infarct size. It seem ed likely that glibenclamide (0.3mg/kg, i.v.), given in combination, reduced the effects of these PCOs, especially KR-30450 (30 ${mu}$g/kg, i.v.) on the infarct size. These results indicate that. in the coronary occluded rat model of ischemia, lemakalim and KR-30450 may exert cardioprotective activity through a reduction of infarct size, the effect being considered related to the opening of K$_{ATP}$ channel.