Theoretical basis of ecologo-floristic classification according to Braun-Blanquet approach is discussed with the special attention to the contribution of Russian scientists. Principal results concern presentation of vegetation continuum in discrete classification units: polymodal conception of plant communities, principle of plural syntaxonomic decisions, pragmatic approach to classification, method of homological rows of plant communities, etc. Current ecologo-floristic classification of vegetation in Russia consists of 77 classes. This system is a good basement for estimation of rarity of plant communities and biodiversity protection. The first variant of "Red Book" of plant communities of Russia and other eastern European countries is discussed.