With nonsmoking, non-OC users serving as the reference group, the odds of cerebral infarc- tion were 1.3 times greater (95% CI, 0.7 2.1) for women who smoked but did not use OCs, 2.1 times greater (95% CI, 1.0 4.5) for nonsmoking OC users, and 7.2 times greater (95% CI, 3.2 16.1) for OC users who smoked.340 There was also a syn- ergistic effect of smoking and OC use on hemorrhagic stroke risk. With nonsmoking, non-OC users as the reference group, the odds of hemorrhagic stroke were 1.6 times greater (95% CI, 1.2 2.0) for women who smoked but did not use OCs, 1.5 times greater (95% CI, 1.1 2.1) for nonsmoking OC users, and 3.7 times greater (95% CI, 2.4 5.7) for OC users who smoked.341 Exposure to environmental tobacco smoke (also referred to as passive or second-hand smoke) is an established risk factor for heart disease.342,343 Exposure to environmental tobacco smoke may also be a risk factor for stroke, with a risk approaching the doubling found for active smoking,344 349 although 1 study found no association.350 Because the dose of exposure to environmental tobacco smoke is substantially lower than for active smoking, the magnitude of the risk associated with environmental tobacco smoke is surpris- ing. This apparent lack of a dose-response relationship may be explained in part by physiological studies suggesting a tobacco smoke exposure threshold rather than a linear dose- Recent studies of the effects of smok- ing bans in communities have also shown that these bans are associated with a reduction in the risk of stroke. After Arizona enacted a statewide ban on smoking in most indoor public places. 