The Chesapeake Bay-Susquehanna River Basins Project of the Federal Water Pollution Control Administration has as its primary objective the development of a comprehensive program for water pollution control in the Chesapeake Bay drainage basin. To permit a better understanding of this complex body of water and to provide a satisfactory means for analysis of present and future pollution problems and selection of optimum control methods, an attempt has been made to model the system in mathematical terms. To mathematically describe the fate of pollutants entering such a tidal system, knowledge of its turbulent dispersion properties is required. To gather this type of information for the upper Potomac estuary, a dye tracer study was carried out by the Project during the 34-day period from June 10 to July 14, 1965. The purpose of the report is to describe the procedure used in this large scale tracer experiment, the results obtained, the methods used in the analysis of these results, and, finally, to present the conclusions reached regarding turbulent dispersion properties of this tidal system.