Five prospective cohort studies were compared in order to evaluate the relationship between type A personality (aggressive behavior) and coronary heart disease (CHD). The Western Collaborative Group Study (WCGS) demonstrated increased risk for CHD in males with type A personality. A follow-up study revealed a greater incidence of second myocardial infarction. The Framingham study showed higher rates of CHD in type A men and women. Two studies, MRFIT and a third evaluation of the WCGS, revealed no relationship between type A personality and CHD and mortality due to CHD. Because the studies disagree in the relationship between type A personality and CHD, it is impossible to conclude that type A personality is a risk for CHD.