The effects of cooling (to 28 °C) on the vasodilation induced by diazoxide (10−9-3 × 10−4 m) on carbachol-pre-contracted calf cardiac vein and coronary artery and the role of nitric oxide in these effects were analyzed. Diazoxide produced concentration-dependent relaxation of calf cardiac vein and coronary artery rings pre-contracted with carbachol (10−6 m). During cooling, the pIC50 values, but not the maximal responses, to diazoxide were significantly lower than at 37 °C in both preparations. Cooling to 28 °C in the presence of NG-nitro-L-arginine methyl ester (10−4 m) did not modify the effect of temperature both in cardiac vein and coronary artery. These results suggest that cooling-induced changes of diazoxide in calf cardiac vein and coronary artery are independent of nitric oxide.