During 2002-04 the U.S. Geological Survey, in cooperation with the Houston-Galveston Area Council and the Texas Commission on Environmental Quality, conducted a systematic monitoring study on Lake Creek, Peach Creek, and Caney Creek near Houston, Texas, to assess the current water-quality and biological conditions in the three tributaries to Lake Houston. Streamflow and water-quality data (chloride and sulfate, nutrients, biochemical oxygen demand, phytoplankton, indicator bacteria, pesticides, and suspended sediment) were collected at 11 sites, and fish and benthic-macroinvertebrate data were collected at eight of the 11 sites. Graphical comparisons of concentration data for eight water-quality constituents by watershed indicate relatively large differences in concentration distribution among all three watersheds for nitrite plus nitrate nitrogen (medians: Lake, 0.20; Peach, 0.14; and Caney, 0.32 mg/L). Graphical comparisons of these data by season show consistency in distribution of constituent concentrations. The distributions of chlorophyll-a in summer and E. coli bacteria in winter each contain a few relatively large concentrations. Fifty-six species of fish from 15 major families were collected during the study. For all sites except one on Lake Creek, the majority of fish collected were sunfish; minnows dominated at the one Lake Creek site. Invertivores (mostly sunfish and minnows) made up more than 65 percent of the trophic structure, omnivores were the next largest percentage, and piscivores the smallest percentage. Ecoregion-specific index of biotic integrity (ECO-IBI) scores (averages of samples) for three of four upstream Lake Creek sites indicate intermediate aquatic life use, and the most downstream site, high aquatic life use. ECO-IBI scores for the Peach Creek and Caney Creek sites indicate high aquatic life use. The maximum number of aquatic-insect taxa (51) were collected at a site on Peach Creek near Cleveland, and the minimum number of aquatic-insect taxa (17) were collected at site on Caney Creek near New Caney. The benthic-macroinvertebrate index of biotic integrity (B-IBI) scores (averages of samples) for the three upstream Lake Creek sites indicate intermediate aquatic life use, and the B-IBI score for the most downstream site indicates high aquatic life use. B-IBI scores for the Peach Creek sites, in downstream order, are exceptional and high; and scores for the Caney Creek sites, in downstream order, are high and intermediate.