The U.S. Geological Survey (USGS) has developed a national database and report on endocrine and reproductive condition in two species of fish collected in U.S. streams and rivers. This information provides scientists with a national basis for comparing results of endocrine measurements in fish from individual sites throughout the country, so that scientists can better ascertain normal levels of biomarkers. The database includes information on several measures of reproductive and endocrine condition for common carp and largemouth bass. Data summaries are provided by reproductive season and geographic region. A national-scale reconnaissance investigation was initiated in 1994 by the USGS that utilized a suite of biological assays (biomarkers) as indicators of reproductive health, and potentially, endocrine disruption in two widely distributed species of teleost (bony) fish, largemouth bass (Micropterus salmoides) and common carp (Cyrinus carpio). The suite of assays included plasma sex-steroid hormones, stage of gonadal development, and plasma vitellogenin, an egg protein that indicates exposure to estrogenic compounds when found in male fish. More than 2,200 common carp and 650 largemouth bass were collected at 119 rivers and streams (fig. 1).