The Chesapeake Bay Environmental Model Package (CBEMP) was used to assess the environmental benefits of a ten-fold increase in native oysters in Chesapeake Bay. The CBEMP consists of a coupled system of models including a three-dimensional hydrodynamic model, a three-dimensional eutrophication model, and a sediment diagenesis model. The existing CBEMP benthos submodel was modified to specifically represent the Virginia oyster, Crassostrea virginica. The ten-fold oyster restoration is computed to increase summer-average, bottom, dissolved oxygen in the deep waters of the bay. Summer-average system-wide surface chlorophyll declines by 1 mg m-3. Filtration of phytoplankton from the water column produces net removal of nitrogen through sediment denitrification and sediment retention. A significant benefit of oyster restoration is enhancement of submerged aquatic vegetation. Calculated summer-average biomass improves by 25% for a ten-fold increase in oyster biomass. Oyster restoration is most beneficial in shallow regions with limited exchange rather than in regions of great depth, large volume and spatial extent.