Field assessments of laboratory-derived water quality criteria were conducted in 520 meter long outdoor experimental streams located in Central Minnesota. The report presents an overview of the published studies. Eight pollutants were tested from 1976 to 1984; duration of pollutant additions lasted from 12 to 75 weeks. Primary emphasis was in measuring community structural changes. Examples of population effects observed were in survival, growth, reproduction, diversity, emergence and behavioral differences. Stream impacts appeared to differ with each pollutant tested. Effects observed on the stream populations were at or above the recommended criteria concentrations. For two pollutants (pentachlorophenol and ammonia nitrogen), no margin of safety was evident. Laboratory-derived criteria and results from single species tests were good predictors of population impacts in the experimental streams. (Copyright (c) 1988 Gordon and Breach Science Publishers Inc.)