DescriptionNew interest has been awakened in recent years in a group of compounds known as steroids and characterized by a common cyclopentanoperhydrophenanthrene nucleus. Summarizing, it can be said that microbial transformations of steroids are growing in importance, and at an increasing rate. Applications in the hormone field are numerous, but better starting materials must be found than the expensive ones used at present. The microbial degradation of cholesterol has been demonstrated as a possibility and a wide range of organisms has been employed. However, the rates of the reactions are very slow and the decomposition is complete to carbon dioxide with few intermediates isolated.