Men incuring coronary heart disease (CHD) during surveillance of an employed population were studied for risk factors associated with additional myocardial infarctions. The coronary-prone Type A behavior pattern measured by a test score, number of cigarettes smoked daily, and serum cholesterol were significantdiscriminators between the 67 men with recurrent CHD and the 220 with but a single clinical CHD event. Diastolic blood pressure and fasting serum triglycerides were not significant discriminators. Statistical analyses directed to possible sources of bias occasioned by the combined retrospective-prospective study design revealed that these problems are negligible and do not alter the findings observed. Type A score appears relatively unaffected by whether the measure was made before or after the initial CHD event. Multivariable discriminant function equations showed Type A score to be the strongest single predictor of recurrent CHD among the variables available. Number of cigarettes smoked and serum cholesterol accounted for additional variance. Future field trials for the secondary prevention of myocardial infarction would be strengthened by consideration of the possible role of Type A behavior.