The clinical, electrocardiographs, angiographic, and hemodynamic features of seven patients with isolated, severe (>75% of diameter) narrowing of a diagonal branch of the left anterior descending artery are presented. The incidence of this entity was 0.5% among patients with arteriosclerotic heart disease undergoing coronary angiography. Angina was severe in two patients, moderate in four, and mild in one. One patient had unstable angina. Stress tests were abnormal in two of three patients. Six patients had normal left ventricular angiograms, and one had a mildly decreased ejection fraction. All patients surviveda meanfollow-up of 18 months (range 6 to 32). No patient suffered a myocardial infarction. Five became asymptomatic on medical therapy; one patient with mild and another with moderate angina were unimproved. This rare anatomic subset of patients with coronary artery disease has a favorable short-term prognosis.