We report the association between hostility and the incidence of ischemic heart disease (IHD) in 3,750 Finnish men aged 40-59. Hostility was assessed from self-ratings on irritability, ease of anger-arousal, and argumentativeness, and four groups were formed from the summed hostility ratings. At baseline, the age-adjusted relative risk (RR) of the prevalence of angina pectoris between the highest and lowest hostility groups was 2.88 (95% confidence limits (CL), range 1.71-4.77). A three-year follow-up yielded 65 deaths and 109 IHD-incident cases. Hostility did not predict IHD among healthy men, but among men with previous IHD and hypertension (N = 104), the age-adjusted RR of IHD between the highest and lowest hostility groups was 12.9 (95% CL, 3.92-42.6). After standardization for smoking, obesity, heavy alcohol use, and snoring, the RR was 14.6 (95% CL, 1.94-110). When the degree of dyspnea at baseline was also standardized, the RR was 21.1 (95% CL, 1.59-282). Our data suggest that extreme hostility is not a consequence of symptom severity; rather, hostility is a strong determinant of coronary attack among hypertensive men with IHD.