A few studies examined interactive effects between air pollution and temperature on health outcomes. In this study, the authors aimed to examine whether temperature modified effects of ozone on cardiovascular mortality in 95 large US cities. The authors separately used a nonparametric regression model and a parametric regression model to explore interactive effects of temperature and ozone on cardiovascular mortality between May and October of the years from 1987 to 2000. The authors used a Bayesian meta-analysis to pool estimates. The nonparametric and parametric regression models both showed that temperature enhanced effects of ozone on mortality, but the effect modification varied across regions. A 10-ppb increment in average ozone concentration at 3 previous days was associated with 0.41% (95% posterior interval [PI]: -0.19%, 0.93%), 0.27% (95% PI: -0.44%, 0.87%), and 1.68% (95% PI: 0.07%, 3.26%) increases in daily cardiovascular mortality corresponding to low, moderate, and high levels of temperature in all 95 US cities, respectively. The authors concluded that temperature modified effects of ozone, particularly in the northern regions.