1. Visual inspection and computer measurement of angiograms are highly correlated with direct examination of atherosclerosis in a specified vessel segment. 2. Computer assessment of an angiogram is highly correlated with cholesterol content of atherosclerosis in a specified vessel segment. 3. Serial change in human atherosclerosis can be measured by angiography. 4. Approximately 50% of men with premature atherosclerosis manifest by myocardial infarction between ages 40 and 49 will show progression in femoral atherosclerosis in one year. An equal number will have lesions which are apparently stable or show regression. 5. Small scale clinical trials employing atheroma regression/progression assessment by angiography are feasible.