Arcytophyllum is a neotropical genus of erect shrubs and prostrate subshrubs containing 15 species. The genus occurs commonly at higher elevations in the Andes of South America from Venezuela to Peru and Bolivia, and in the mountains of Panama and Costa Rica in Central America. This volume sets out a new infraspecific interpretation of Arcytophyllum. Several new synonymies are presented, as well as a key to the entire genus. A history of the genus, and discussions of the orthography of the generic name and of the ecology and distribution of the genus are also included.