An analysis was made of correlative factors which might be related to the angiographically measured extent of coronary artery disease in 140 patients. All patients presented with clinically important chest pain. Thirty-three had a normal coronary arteriogram. The extent of the atheromatous process was measured precisely at angiography by three different techniques. A coronary score, based on the percentage of luminal narrowing, was found to be best suited for the analysis. The most important contributory factors to the severity of atherosclerosis was duration of clinical history, number of previous myocardial infarctions, and male sex, but more specifically elevation of serum cholesterol and diabetes mellitus. Cigarette smoking, obesity, hypertension, a family history of atherosclerosis, and elevated serum triglycerides had a positive influence but this was not statistically significant.