The monograph contains an overview of the principles and methods of classification and classification systems of various geobotanical schools. Some logical classification issues are discussed, an analysis of the features of the vegetation cover as an object of classification is given, and an overview of phytocenotic units allocated in the vegetation cover is given in order to classify them. The history and current state of the issue of vegetation classification in the Scandinavian and Baltic countries, in Central and Southern Europe, in the USA and in the USSR is presented. The problem of classification of vegetation cover taking into account its dynamics is considered. A summary of mathematical methods for classifying plant communities is provided. The question of the naturalness of classification and the choice of defining features is discussed.