This dataset contains information on the cluster characteristics, health effect estimates, and the meta-regression results. This dataset is associated with the following publication: Baxter, L., J. Crooks, and J. Sacks. Influence of exposure differences on city-to-city heterogeneity in PM2.5-mortality associations in US cities. ENVIRONMENTAL HEALTH. Academic Press Incorporated, Orlando, FL, USA, 16(1): 1-8, (2017).