Glucose tolerance tests and cortisone glucose tolerance tests have been carried out in 41 patients with documented myocardial infarction, and the results have been compared with those obtained from a similar group of hospital patients without manifest coronary artery disease. Results of both tests have indicated that patients with a previous myocardial infarction have a higher fasting blood glucose concentration, and do not dispose of an oral glucose load so efficiently. In addition, serum levels of total lipids, cholesterol and triglycerides were significantly elevated in patients with arteriosclerotic heart disease. Although patients with an abnormal glucose tolerance test had a higher mean serum triglyceride concentration, there was considerable overlap, and no statistically significant relationship could be demonstrated between carbohydrate intolerance and hyperlipemia. It is suggested that the apparent presence of minimal abnormalities of carbohydrate metabolism in a significant number of patients with arteriosclerotic heart disease warrants further consideration as a possible factor in the development of atherosclerosis.