The metabolic N-oxidation ofnitrogeusxebiotics has been reported tc occur in many biologicalsystems, in addition to mammaliantissues, and the mechanisms appear to differ in many respects from those involved in oxidative attack atcarbon centres. Theextensive useofnitrogen-containing compounds as pharmaceuticals and chemical intermediates can lead to exposure to alarge numberofthese agentsunderwidelyvaryingconditions. Biotransformation of these xebiotics by N-oxidative pathways can effect detoxication, butequallywellcaninduceformation ofcytotoxicmetabolites or potential promutagens and procarcigens. The substantial progress, in recent years, in our understanding ofthe biochemistry and toxicology of N- oxidation of nitrogeus structures has created a need for a synthesis of current kwledge. This book provides a wide-ranging review of the state-of-the-art in nitrogen xebiochemistry divided into four parts. The introductory chapter discusses recent developments in trace analysis of radical intermediates and other N-oxygenated products by physical and immuchemical techniques. Special attention is given in Part Two to the enzymology of N-oxidation. Thus, detailed account is given of the mechanism and substrate specificity of the flavin-containing mo- oxygenase and factors regulating its activity are addressed. A separate chapter outlines the polymorphic expression of flavoprotein-dependent reactions. Similarly, the mechanistic background and inducibility of cytochrome P-450-catalysed turver of specific types of nitrogeus compounds is highlighted. Data are also compiled describing the role of peroxidative N-oxidation of xebiotics in extrahepatic tissues lacking significant amounts ofcytochrome P-450.