Terrestrial microcosms have been used for several decades by researchers to evaluate the fate and transport of xenobiotics in the environment; however, very little information is available on their application to the fate, survival, and transport of recombinant bacteria and microbial pest control agents. The research included in the document represents the current scientific information available regarding the applicability of terrestrial microcosms and related methodologies for evaluating detection methods and the fate and survival of microorganisms in the environment. The three terrestrial microcosms described in this document were used to evaluate the survival and fate of recombinant bacteria in soils and in association with plant surfaces and insects and their transport through soil with percolating water and root systems, and to test new methods and procedures to improve detection and enumeration of bacteria in soil. The usefulness of these various microcosms as a tool for risk assessment is underscored by the ease in obtaining soil from a proposed field release site to evaluate subsequent Genetically Engineered Microorganisms' fate and survival.