Stereochemistry is defined as the study of the three-dimensional structure of molecules. Stereochemical considerations are important in both isomerism and studies of the mechanisms of chemical reactions. Concentrating on organic chemistry, early chapters deal mainly with definitions of terms such as chirality, enantiomers, diastereoisomers and racemisation, complete with suitable examples to illustrate key concepts. Use of a polarimeter and associated definitions are described, together with two different conventions D, L and R, S for specification of configuration. The distinction between conformation and configuration is developed to include assignment onf configurations to di-substituted cyclohexanes and to the decalins. Aspects of stereochemistry are explored through consideration of addition reactions to alkenes and carbonyl groups, nucleophilic substitution, and reactions (and interactions) involved in the resolution of racemic mixtures.