Angiographic, clinical, and five-year follow-up study of 20 cases of myocardial infarction with normal coronary angiograms (MI-NCA) and 20 cases of myocardial infarction with single vessel obstruction (MI-SVO) are presented. MI-SVO patients differed from MI-NCA in being older (53.7 vs 44.5 years, p = 0.025), predominantly male (90 percent vs 40 percent, p = 0.001), frequently having large left ventricular akinetic segments (50 percent vs 15 percent, p = 0.01), and frequently having antecedent typical angina (55 percent). MI-NCA was more frequently associated with definite mitral valve prolapse (25 percent vs 10 percent, NS); migraine, or Raynaud's phenomenon (45 percent vs 5 percent, p = 0.001); birth control pill ingestion in women (33 percent vs 0 percent, p = 0.05); paroxysmal atrial flutter (25 percent vs 0 percent, p = 0.01); and antecedent atypical angina (25 percent). Frequency of cigarette smoking and hypertension and the mean serum cholesterol levels were similar in both groups. On follow-up, MI-NCA patients more commonly had neurologic events (25 percent vs 5 percent, p = 0.05) and second myocardial infarction (15 percent vs 0 percent, p = 0.02), but deaths occurred infrequently in both groups. These data suggest a variety of pathophysiologic causes for MI-NCA.