The mortality attributable to ischemic heart disease as a result of cigarette smoking is greater of a community of older adults in southern California, the authors tested the hypothesis that nonsmoking women exposed to their husband's cigarette smoke would have an elevated risk of fatal ischemic heart disease. Married women aged 50-79 years who had never smoked cigarettes (n = 695) were classified according to the husband's self-reported smoking status at entry into the study: never, former, or current smoker. After 10 years, nonsmoking wives of current or former cigarette smokers had a higher total (p less than or equal to 0.05) and age-adjusted (p less than or equal to 0.10) death rate from ischemic heart disease than women whose husbands never smoked. After adjustment for differences in risk factors for heart disease, the relative risk for death from ischemic heart disease in nonsmoking women married to current or former cigarette smokers was 14.9 (p less than or equal to 0.10). These data are compatible with the hypothesis that passive cigarette smoking carries an excess risk of fatal ischemic heart disease.