Nonpoint source (NPS) runoff from mining, landfills, roads, croplands, grazing lands, and forests can contain chemicals harmful to aquatic organisms. Full scale biological surveys to determine their effects are difficult and costly. Bioassays of environmental samples integrate the effects of all toxicants contained in a sample. Biological organisms are being used more frequently to identify toxicant problems and to rank-order their severity. The Corvallis Environmental Research Lab has developed a multi-media bioassessment protocol to assist in the identification of toxicity potentials associated with waste disposal. Similar techniques can be used to identify NPS pollutants. The bioassay response indicators are particularly useful in identification of field-site problems where complex mixtures of pollutants might be present. Use of the bioassessment protocol reduces the initial need for extensive chemical analyses, and produces data in a form more readily understood by the public than bulk chemical concentrations.