Many compounds have been marketed for control of zebra mussels (Dreissena polymorpha), but most compounds lack comparable toxicity data and have not been tested on nontarget organisms. This study tests the toxicity of 18 chemicals to two sizes of zebra mussels, two nontarget fish (rainbow trout, Oncorhynchus mykiss and channel catfish, Ictalurus punctatus), and a unionid mussel (threehorn wartyback, Obliquaria reflexa) under standard conditions