The Toxic Substances Control Act (TSCA) gives the EPA Office of Toxic Substances (OTS) jurisdiction over the manufacture, processing, distribution, use, and disposal of all microbial biotechnology products intended for, or already in, commerce not specifically subject to other federal regulatory authorities. OTS reviews biotechnology products for two classes of microorganisms: those for use in closed systems, such as fermentors and those for intentional environmental release. Examples of products reviewed in OTS include enzymes, such as proteases produced by bacteria in fermentation systems and re-combinant rhizobia for enhanced nitrogen fixation in legumes. Hazard and exposure analyses are combined with other considerations into an overall risk assessment for each product. Hazard analyses focus on potential adverse human and environmental effects. Exposure analyses examine the exposure to and fate of the microbe in the environment. The elements of a risk assessment are reviewed, and specific recombinant microorganism risk assessments are discussed.