Coronary vasomotor response to acetylcholine infusion was studied in a 69-year-old currently smoking man with enhanced insulin response to oral glucose load. Coronary angiogram showed no significant stenoses. Immediately after 20 microg acetylcholine infusion in the right coronary artery, angiographic no-flow, ischemic electrocardiographic changes, and anginal pain developed in the absence of epicardial coronary obstruction. While intracoronary infusion of isosorbide dinitrate was only partially effective, intracoronary infusion of nicorandil, an agent known to improve coronary microcirculation, completely resolved these changes. This is the first case reported so far suggesting that enhanced insulin response may be associated with acetylcholine-induced microvascular vasoconstriction. Microvascular vasoconstriction must be considered when a patient with insulin resistance presents with chest pain.