The document, containing data on the toxicity of chemicals to fish, is in two parts. Part 1 consists of a 1953 study by E.M. Wood, U.S. Fish and Wildlife Service, Kearneysville, West Virginia. Data are compiled on over 3400 Chemicals (mostly organic compounds) which were tested using trout, bluegill, yellow perch, and goldfish, at a 5 mg/L screening concentration. Those compounds producing toxicity at 5 mg/L were tested further at lower concentrations. Part 2 contains data developed during a 1954 study by E.H. Hollis and R.E. Lennon at the Kearneysville laboratory using the same fish toxicity screening test protocols. Parts 1 and 2 are published here for the first time. These documents were prepared at the National Fisheries Research Center, U.S. Fish and Wildlife Service Laboratory, La Crosse, Wisconsin, from original records. A preface has been prepared by R.L. Lipnick, Office of Toxic substances, EPA, reviewing the use of these data in the development of structure-activity relationships and quantitative structure-activity relationships.