The overall objectives are (1) to explore the bacterial metabolism of steroid hormones excreted in the bile, including a description of the metabolic pathways, and (2) to isolate and identify the organisms involved in this metabolism. The identification of bacteria synthesizing the specific enzymes is the key to further inquiries into the biological role, including possible carcinogenesis, of the metabolites. Moreover, understanding of the formation of metabolites also provides an opportunity for controlling them, should it be desirable.