An attempt has been made to attract contributions which illustrate the importance of certain enzymatic processes involved in steroid biosynthesis and metabolism and, in some cases, leading to steroidal action in target sites. Investigators actively engaged in research in such areas were invited to present their material in a manner which they considered fitting. It is hoped that as a result if this, the publication will possess sufficient depth to warrant approval. The blend of review material and experimental data originating in the author laboratories will, it is felt, make for useful reading.