The Clean Water Act has necessitated further requirements and revisions in the industrial permit program maintained under the National Pollutant Discharge Elimination System (NPDES). It is now evident that in many cases the identification and control of toxic substances cannot be accomplished solely on the basis of an effluent guideline approach, emphasizing the need for reliable and economical procedures with which to quantify directly the net toxicity of complex effluents and estimate acute and chronic effects on aquatic biota. Therefore, the major objective of this investigation was to develop and evaluate fish and amphibian embryo-larval test procedures for the toxicogical characterization of municipal and industrial effluents.