Diabetic patients with acute coronary syndromes are at higher risk for mortality, even if they have ST-segment elevation myocardial infarction. Diabetic patients with unstable angina/non–Q-wave infarction have impaired platelet responsiveness to nitric oxide, a physiological anti-aggregating autocoid. The extent of this impairment depends on the degree of hyperglycemia. Rapid correction of hyperglycemia with infused insulin restores responsiveness to nitric oxide, thus ameliorating platelet dysfunction.