The U.S. Geological Survey and the Michigan Depart-ment of Environmental Quality (MDEQ) jointly monitored for selected water-quality constituents and properties of inland lakes during 2001-10 as part of Michigan's Lake Water-Qual-ity Assessment program. During 2001-10, 866 lake basins from 729 inland lakes greater than 25 acres were monitored for baseline water-quality conditions and trophic status. This report summarizes the water-quality characteristics and trophic conditions of the monitored lakes throughout the State; the data include vertical-profile measurements, nutrient measure-ments at three discrete depths, Secchi-disk transparency (SDT) measurements, and chlorophyll a measurements for the spring and summer, with major ions and other chemical indicators measured during the spring at mid-depth and color during the summer from near-surface samples.