BACKGROUND: Few prospective studies have investigated the relationship between spousal cigarette smoking and the risk of incident stroke. METHODS: Stroke-free participants in the U.S.-based Health and Retirement Study (HRS) aged >or=50 years and married at baseline (n=16,225) were followed, on average, 9.1 years between 1992 and 2006) for proxy or self-report of first stroke (1,130 events). Participants were stratified by gender and own smoking status (never-smokers, former smokers, or current smokers), and the relationship assessed between the spouse's smoking status and the risk of incident stroke. Analyses were conducted in 2007 with Cox proportional hazards models. All models were adjusted for age; race; Hispanic ethnicity; Southern birthstate; parental education; paternal occupation class; years of education; baseline income; baseline wealth; obesity; overweight; alcohol use; and diagnosed hypertension, diabetes, or heart disease. RESULTS: Having a spouse who currently smoked was associated with an increased risk of first stroke among never-smokers (hazard ratio=1.42, 95% CI=1.05, 1.93) and former smokers (hazard ratio=1.72, 95% CI=1.33, 2.22). Former smokers married to current smokers had a stroke risk similar to respondents who themselves smoked. CONCLUSIONS: Spousal smoking poses important stroke risks for never-smokers and former smokers. The health benefits of quitting smoking likely extend to both the individual smoker and his or her spouse.