The Malagasy endemic genus Calyptranthera (Asclepiadaceae) is revised. Five species are recognized. Four new species are described, viz. C. baronii, C. brevicaudata, C. grandiflora and C. pubipetala. The morphological structure of the flower is discussed and a key, descriptions, the distribution and drawings of all taxa are given. A hypothesis of the cladistic relationship of the species is presented. Phytogeography and vicariance patterns are discussed.