Broad agreement on specific approaches or standardized test batteries for assessing behavioral toxicity is unlikely to emerge in the foreseeable future. EPA should reject test standardization in any case, however; standardization stifles progress and, in addition, may bypass unique properties of new types of substances. The optimal strategy is to prescribe a set of functions, such as sensory, motor, and complex performance processes, leaving it to the manufacturer to select adequate tasks. Adequacy would be judged by EPA staff, in consultation with advisory panels, and resolved, in most cases, by a dialogue with the manufacturer.