This volume looks in detail at the chemistry and carcinogenicity of the cyclopenta[a]phenanthrenes; these are fully aromatic (i.e. dehydrogenated) derivatives of physiologically important hormones, the steroids and some have been shown to be powerful carcinogens in animal models. Others have been found to be of widespread occurrence in the environment where they are probably derived from plant steroids. This book covers all aspects of this class of compounds including their chemical syntheses and chemistry, occurrence, physical and spectral properties, metabolism, carcinogenicity and mutagenicity. It also outlines how steroid biochemistry indicates the way in which these molecules might be formed in vivo as a result of incorrect steroid metabolism and ends with a call for the application of powerful modern analytical techniques to the problem of whether they do occur in this way and are a cause of human cancer.