BACKGROUND Relatively few studies have been focused on the effect of smoking among older individuals. The goal of this study is to investigate the relationship between smoking status and cause-and age-specific mortality among elderly women. METHODS Women aged 65 years and older and living in four geographical areas (Baltimore, Md, Minneapolis, Minn, Pittsburgh, Pa, and Portland, Ore) were recruited from various population-based listings for participation in the multicenter Study of Osteoporotic Fractures between September 1986 and October 1988 (N=9704). During a mean follow-up of 4.9 years (<99% complete), 751 deaths occurred. The date and cause of death were ascertained, and the relationship between mortality and current and past smoking status was analyzed using Cox proportional hazards modeling techniques. RESULTS Compared with nonsmokers, women smokers aged 65 to 74 years have a more than twofold increase in mortality attributable to increases in both cardiovascular and cancer mortality; death from smoking-related cancers increased eight- to 10-fold. Women 75 years and older who smoke have a small overall increased relative risk (RR) of mortality (RR=1.4; 95% confidence interval [CI], 0.9 to 2.3), but more than five-fold increased risk of dying from a smoking-related cancer (RR=5.2; 95% CI, 1.6 to 16.8). All-cause and cardiovascular death rates approach those of nonsmokers within 10 years after a woman quits smoking; morality from smoking-related cancers remains elevated for at least 23 years. CONCLUSIONS The harmful effects of continuing to smoke are apparent even among women aged 75 years and older.