Prospective studies have suggested that antisocial Type A personality traits may be associated with an increased incidence of coronary heart disease (CHD). However, few data have addressed whether more favorable personality characteristics may be inversely correlated with CHD. Therefore, two standardized questionnaires designed to either assess anger and hostility or to measure the propensity to laugh under a variety of situations encountered in everyday life, were administered to 300 consecutive subjects. Compared to controls, CHD subjects were significantly less likely to experience laughter during daily activities, surprise situations or social interactions (P<0.005). Logistic regression analysis revealed an inverse correlation between humor and CHD, even after adjustment for other covariates, including hypercholesterolemia, hypertension and diabetes mellitus (P=0.03). A significant inverse association was also observed between humor production and antisocial Type A personality traits (P=0.0001). These data extend previous observations linking antisocial Type A personality traits to CHD and raise the possibility that the propensity to laugh may contribute to cardioprotection.