The hydrologic settings of 150 randomly-selected lakes in the north-central United States were investigated by principal component analysis as a first attempt to develop a general classification of the hydrologic setting of lakes. Precipitation-evaporation balance and the water quality parameters have high factor loadings on the first principal component. Highest loadings on component 2 are for streamflow in and out of the lakes. Components 3 and 4 are characterized by geology and ground-water flow parameters. The drainage basin area/lake area ratio, the overland runoff parameter, has the highest loading on component 5.