ISEE-67 Introduction/Aim: Ozone has been linked to many adverse health effects, however some time-series studies found a relationship between ozone levels and mortality, while others found inconclusive or null effects. To help resolve the potentially conflicting results of numerous studies, we performed a meta-analysis of time-series studies of ozone and mortality. Methods: A systematic review of the literature identified 39 individual time-series studies and 144 separate effect estimates that met our protocol. We estimated pooled effects by combining information across locations using a two-stage Bayesian hierarchical model. Results were compared for cause-specific mortality (total, cardiovascular, and respiratory), location, potential confounding by particulate matter, season, age group (all ages or the elderly), and lag structure. Results: Results indicate that a 10 ppb increase in daily ozone at single-day or two-day average of lags 0, 1, or 2 days is associated with an 0.83 (95% posterior interval: 0.53, 1.12%) increase in total mortality. The pooled effect for cardiovascular and respiratory mortality combined was slightly higher than the overall effect for total mortality. Pooled effect estimates using U.S. and non-U.S. studies were roughly similar. Results were robust to adjustment by particulate matter. Pooled estimates for lags of 0 or 1 days were larger when only a single lag estimate was reported as opposed to when multiple lags were reported, indicating potential publication bias. We compared results from the meta-analysis to those of our recent multi-city time-series study of ozone and mortality based on 95 urban centres in the U.S., which is part of the National Morbidity, Mortality, and Air Pollution Study (NMMAPS). The meta-analysis results were consistently larger than the NMMAPS, which could be indicative of publication bias, or could result from methodological differences or other factors. Conclusion: Results from this meta-analysis indicate an elevated mortality risk from short-term exposure to ambient ozone. These results do not appear to be confounded by location or particulate matter. This work provides further evidence for the harmful effects of ozone on human health.