The authors assessed the effect of psychological stress on total and cause-specific mortality among men and women. In 1981-1983, the 12,128 Danish participants in the Copenhagen City Heart Study were asked two questions on stress intensity and frequency and were followed in a nationwide registry until 2004, with <0.1% loss to follow-up. Sex differences were found in the relations between stress and mortality (p = 0.02). After adjustments, men with high stress versus low stress had higher all-cause mortality (hazard ratio (HR) = 1.32, 95% confidence interval (CI): 1.15, 1.52). This finding was most pronounced for deaths due to respiratory diseases (high vs. low stress: HR = 1.79, 95% CI: 1.10, 2.91), external causes (HR = 3.07, 95% CI: 1.65, 5.71), and suicide (HR = 5.91, 95% CI: 2.47, 14.16). High stress was related to a 2.59 (95% CI: 1.20, 5.61) higher risk of ischemic heart disease mortality for younger, but not older, men. In general, the effects of stress were most pronounced among younger and healthier men. No associations were found between stress and mortality among women, except among younger women with high stress, who experienced lower cancer mortality (HR = 0.51, 95% CI: 0.28, 0.92). Future preventive strategies may be targeted toward stress as a risk factor for premature death among middle-aged, presumably healthy men.