Аннотация:The first part of the lecture deals with different approaches of representation, formal mathematical description and classification of reactions in organic chemistry. Different model-driven (Ugi, Arens, Vladutz, Fujita, Hendrickson, etc) and data driven (Gelernter, InfoChem, etc) methods of reaction classification are considered. Dujundji-Ugi matrix formalism and Tratch-Zefirov’s formal-logical approach to mathematical description and enumeration of organic reactions are discussed in details. Representations of reaction mechanisms, chain and organometallic catalytic reactions are also touched upon. The principles of enumeration of organic reactions are considered. Programs SYMBEQ and IGOR for generating and discovering novel organic reactions are mentioned. After that the most important notions and basic principles of computer-aided synthesis design are discussed. Empirical and nonempirical approaches to it are considered. The most popular approaches and corresponding software (LHASA, SECS, SYNCHEM, CAOS, EROS, SYNGEN) are touched upon. Reaction prediction program CAMEO is also considered.