The present paper aims at introducting Dahlgren’s system of classification of the angiosperms.  Phenetic and phylogenetic classifications are discussed.  The basic principles and methods used by Dahlgren are explained.  Dahlgren’s opinions on some important problems,  such as the origin of angiosperms,  the flowers of primitive angiosperms,  the relation between the dicotyledons and monocotyledons,  the origin of the monocotyledons,  the treatment of the “Amentiferae” and of the orders of the “Sympetalae”,  are all expressed.  A brief comparison between Dahlgren’s system and three other current systems,  viz. those of Takhtajan,  Cronquist and Thorne is also given.