The recent history of loading of total phosphorus (TP) and nitrogen (N) species to Onondaga Lake, NY, from an adjoining domestic waste treatment facility (METRO), and related impacts on die lake, are documented. The discharge from METRO represents an extraordinary contribution to the inflow of the lake; e.g., in most years it is the largest source of water during the month of August. Approximately a 20-fold reduction in effluent TP concentration has been achieved by METRO over die 1970–1993 period, in response to a detergent ban and increased levels of treatment. The TP loading from the facility decreased about 5-fold over the 1977–1992 interval. A significant level of nitrification has been achieved during die warmer mondis since the late 1980s, but this has been attended by increased effluent concentrations of nitrite (NO−2). METRO presently contributes approximately 60, 90, and 80% of the total external loads of TP, ammonia, and total N, respectively. The extremely high prevailing external total loads of TP and total N, approximately 8 and 200 g/m2/y, respectively, severely impact die lake. Recurring degradations associated with the cultural eutrophication of the lake include excessive concentrations of phytoplankton, poor clarity, rapid loss of oxygen from die hypolimnion, and lake-wide oxygen depletion during die fall mixing period. Related water quality standards for transparency and oxygen are violated. A state guidance value for summer epilimnetic TP concentration of 20 μg/L is exceeded by a factor of ≥ 3 annually. Standards to protect aquatic life against the toxic effects of free ammonia and NO−2are violated by a large margin routinely in die upper waters in summer. METRO is die appropriate focus for related remediation efforts.