E.P.A. needs effective, reliable, rapid, and relatively inexpensive tools and techniques to screen and identify those chemicals having potentially harmful health and ecological effects. In addition to data on direct organisms or system impacts, effective techniques should provide information on accumulation, persistence and degradation, and the potential for intermedia transport. With additional evaluation, documentation, and development, current microcosm technology should be extremely useful in meeting this need. Copyright (c) Gordon and Breach Science Publishers Ltd., 1976.