Disease, mortality, and growth of benthic organisms can be influenced by and determine spatial distributions. The eastern oyster, Crassostrea virginica, an economically and ecologically important species in Chesapeake Bay, is found in both the intertidal and subtidal in Virginia, but only in the subtidal in Maryland. I used field experiments and sampling to determine whether disease (Dermo) mortality, and growth of oysters vary among tidal heights during summer in the Maryland and Virginia regions of Chesapeake Bay. Results indicated that Dermo prevalence and mortality decreased and growth increased with decreasing durations of intertidal air-exposure. Dermo prevalence was higher in habitats with long durations of air-exposure than in subtidal habitats but progression of the disease did not differ consistently among tidal heights. Patterns in summer mortality, growth, and disease in combination with recruitment, winter mortality, and predation likely contribute to the variation in tidal distributions of oysters within Chesapeake Bay.