The book is devoted to an important aspect of pharmacology and pharmaceutical chemistry, i.e. the significance of stereoisomerism of drugs for their biological effect from the point of view of their pharmacokinetics, pharmacodynamics and toxicology. The authors review the landmarks in the development of stereochemistry and stereopharmacology. Present-day IUPAC terminology is discussed; general issues of stereoisomerism are considered including separation of racemic mixtures and asymmetric synthesis of isomers, methods of quantifying the isomers of a drug in biological material. The authors put special emphasis on general problems of the influence of stereoisomerism on pharmacological and adverse effects of drugs. A classification of drugs based on stereochemical properties of their isomers is proposed. Possibilities of interaction of stereoisomers in racemic mixtures are discussed.