This study explored the association between Type A behavior, as measured by a short questionnaire on time urgency and competitiveness, and the development of coronary heart disease (CHD). An assessment of Type A behavior in 750 women and 580 men, aged 45-64 years, participating in the Framingham Heart Study, took place between 1965 and 1969. Type A behavior was associated with a two-fold risk of developing CHD over the ensuing 10 years. Among all women, the relative risk (RR) was 2.0 with confidence limits = 1.2 to 3.3. Among housewives, CHD incidence rates were 2.5 times greater among Type A's compared to Type B's (p = 0.02). Type A working women were more than 1.5 times as likely to develop CHD as Type B's, although this was not significant at the 10 year follow-up. Among men employed in white-collar jobs, the RR was 2.4 with confidence limits = 1.1 to 5.7. Type A behavior was most strongly related to coronary diagnoses in which angina pectoris symptoms were present. Synergism between Type A behavior and other CHD risk factors is demonstrated. The findings suggest that assessment of Type A behavior can improve the prediction of incident coronary cases, independent of the standard coronary risk factors.