The report contains the proceedings of a symposium-workshop sponsored by the EPA Gulf Breeze Environmental Research Laboratory to determine the possible impact of artificially introducing microbial insect control agents or oil-degrading agents into the aquatic environment. The efficacy and safety testing, especially against non-target aquatic organisms, for use of bacteria, viruses, fungi, and protozoa to control aquatic insect pests is discussed with remarks of panel members representing government, academia, and industry. Special attention is given to persistence of pathogens in aquatic environments as well as control of aquatic weeds and other non-insect pests. The use of microorganisms to clean up oil spills in aquatic environments is discussed by industrial, academic, and governmental scientists. Special considerations are given to selection of hydrocarbonoclastic microorganisms and use of these microorganisms in special environments--Arctic regions and Louisiana salt marshes.