Reconnaissance limnological and lakebed-sediment surveys were conducted in Connecticut during 1989-91 by the U.S. Geological Survey, in cooperation with the Connecticut Department of Environmental Protec- tion, to evaluate water-quality characteristics of selected public recreational lakes and ponds in the State. Limnological surveys were conducted on 49 lakes and ponds selected from a list of 105 publicly owned waterbodies that qualified for water- quality assessments under Section 314 of the Federal Clean Water Act. Lakebed-sediment surveys were conducted in 9 river impoundments and 1 riverine lake below industrial areas and 2 headwater lakes in relatively pristine areas. The limnological surveys consisted of two sampling events--during spring turnover and during the summer stratifi- cation. Each sampling event included depth profiles of water temperature, specific conductance, hydrogen-ion activity, and dissolved oxygen concen- trations; measurements of Secchi disc transparency; and the collection of samples for the analyses of alkalinity, chlorophyll, phosphorus, and nitrogen concentrations. Areal extent and population density of the dominant aquatic macrophytes were qualita- tively noted during the summer sampling event. These water-quality data were used to determine the trophic classification and acidification status of the 49 lakes. The trophic classification yielded the following results: 2 oligotrophic, 8 early mesotrophic, 13 mesotrophic, 5 late mesotrophic, 10 eutrophic, and 11 highly eutrophic lakes. In terms of acidification status, 7 lakes were classified as acid threatened and 42 as not threatened. A Wilcoxon two-tailed signed rank test was used to compare data for 13 lakes and ponds from the present survey with data from the 1973-75 or 1978-79 surveys conducted by the Connecticut Agricultural Experiment Station and Connecticut Department of Environmental Protection. The test showed no significant difference at the 90 percent confidence level for spring nitrogen and summer chlorophyll-a concen- trations, a significant increase at the 90 percent confidence level in summer phosphorus concentra- tions, and a significant decrease at the 95 percent confidence level in summer transparency. For the lakebed-sediment surveys, composite-grab samples were collected from the deepest part of each lake. Samples were analyzed for arsenic, cyanide, organic and inorganic carbon, selected metals, and methylene-extractable, synthetic organic compounds classified by the U.S. Environmental Protection Agency as semi-volatile priority pollutants. Hanover Pond, Eagleville Lake, and West Thompson Lake had three of the four highest concentrations of cadmium, chromium, copper, lead, nickel, zinc, and cyanide. The four lakes with the highest concentrations of arsenic (Aspinook Pond, Fitchville Pond, Mashapaug Pond, and West Thompson Lake) are located in the eastern part of Connecticut. The three samples with the highest mercury concentrations were from Lake Lillinonah and Lake Zoar. There appears to be a positive correlation between the concentrations of cadmium, chromium, copper, lead, nickel, zinc, and cyanide. Only 15 of the 54 synthetic organic compounds analyzed for were detected in 9 of the 12 lakes sampled. Of these 15 compounds, 14 are polycyclic aromatic hydrocarbons and the 15th is a phthalate ester. Hanover Pond had the most compounds detected (9), and phenanthrene was the compound detected in the most lakes (8).