A nine-month water quality monitoring program was performed on seven lakes in Snohomish County, Washington to: (1) assess current lake quality, (2) identify potential pollutant loading sources, and (3) recommend appropriate restoration/management strategies. A major concern was the extent to which shoreline on-site wastewater systems were adversely affecting quality of the lakes. Two comprehensive septic leachate surveys of lake shoreline were performed to identify the number of concentrated effluent plumes to the lakes and characterize phosphorus loading from this source. A portable fluorometer specifically indexed to degradation products of wastewater was used with great effectiveness in the surveys. Initial fluorometer screening was followed by surface water and shallow groundwater quality sampling/analyses, site inspections/homeowner interviews, and dye testing to corroborate onsite system failures. Open-water areas of the lakes exhibited good to excellent water quality. However, several localized shallow shoreline areas evinced signs of incipient water quality degradation and coincided with effluent plumes from inadequately treated residential wastewater and discharges of surface water drainage. Management efforts were recommended to minimize pollutant loading by both the above sources.