Detailed studies by the Chesapeake Technical Support Laboratory (CTSL) of the Federal Water Quality Administration to define the interrelationships among wastewater inflow, freshwater inflow, and water quality in the Potomac Estuary were undertaken in November 1969. These studies had two purposes: (1) to refine the allowable oxygen demanding and nutrient loadings previously established and (2) to determine the feasibility of using the estuary as a municipal water supply source. Presented herein is a summary of numerous reports published by CTSL with major emphasis on the eutrophication control aspects developed in the recent studies.