The test series developed methods for testing a compliment of aquatic organisms in a single test that satisfies the freshwater acute toxicity requirements for setting water quality criteria. Species tested included fathead minnows Pimephales promelas, rainbow trout Salmo gairdneri, bluegill Lepomis macrochirus, channel catfish Ictalurus punctatus, goldfish Carassius auratus, white sucker Catostomus commersoni, daphnia Daphnia magna, midge Tanytarsus dissimilis, crayfish Orconectes immunis, snail Aplexa hypnorum, tadpole Xenopus laevis, and leech Nephelopsis obscura. Five to nine of the preceding species were simultaneously exposed in individual tests. The chemicals tested were acrolein, aniline, dibutylfumarate, 2,4-dinitrophenol, Guthion, nicotine sulfate, phenol, rotenone, silver, Systox, 1,2,4-trichlorobenzene, 2,4,6-trichlorophenol and o-xylene. The method of simultaneously exposing aquatic organisms in separate compartments of each exposure tank allows more accurate comparisons of species sensitivity with a tested chemical.