Growing evidence suggests that exposure to environmental tobacco smoke may have deleterious cardiovascular effects. Few studies have investigated environmental tobacco smoke exposure in relation to stroke. The authors examined the association between smoking by husbands and stroke prevalence among women nonsmokers in Shanghai, China, where two thirds of men but few women smoke. They analyzed baseline survey data (1997-2000) from a population-based cohort study, the Shanghai Women's Health Study. A total of 60,377 eligible women (aged 40-70 years) were included in the analysis. Information on husbands' smoking status and history of physician-diagnosed stroke was obtained through in-person interviews. Logistic regression was used to compute odds ratios for the associations. There were 526 prevalent cases of stroke reported. The adjusted odds ratios of stroke in women associated with husbands' current smoking of 1-9, 10-19, and > or =20 cigarettes per day were 1.28 (95% confidence interval: 0.92, 1.77), 1.32 (95% confidence interval: 1.01, 1.72), and 1.62 (95% confidence interval: 1.28, 2.05), respectively (p for trend = 0.0002). Prevalence of stroke also increased with increasing duration of husbands' smoking. The authors found that women nonsmokers who lived with husbands who smoked had an elevated prevalence of stroke, and prevalence increased with increasing intensity and duration of husbands' smoking.