OBJECTIVE Epoxyeicosatrienoic acids have been recognized for their protective effects on the cardiovascular system. This study investigated whether two common polymorphisms in genes believed to be influential in regulating circulating levels of epoxyeicosatrienoic acids, namely cytochrome P450 2J2 (CYP2J2) G-50T and soluble epoxide hydrolase (EPHX2) G860A, were associated with ischemic stroke risk in a Chinese population. METHODS AND RESULTS Screening of 200 patients with ischemic stroke and 350 control participants revealed that CYP2J2-50T allele frequency was not significantly different in ischemic stroke cases versus controls. In contrast, EPHX2 860A allele frequency was 16.8% in ischemic stroke cases versus 21.7% in controls (P=0.047), and the presence of this variant allele was associated with a significantly lower risk of ischemic stroke after adjustment for sex, age and multiple cardiovascular risk factors (adjusted odds ratio=0.50, 95% confidence interval 0.29-0.86). Moreover, there was a significant interaction between the EPHX2 G860A polymorphism, smoking and ischemic stroke risk such that nonsmokers carrying the EPHX2 G860A variant allele were at the lowest risk of ischemic stroke (odds ratio=0.33, 95% confidence interval, 0.17-0.67, P=0.002), whereas no significant association was observed in smokers. CONCLUSIONS Collectively, these data indicate a protective influence of the G860A polymorphism of EPHX2 on ischemic stroke in Chinese nonsmokers.