This monograph deals with the systematics and phylogeny of the genus Pyrrosia (Polypodiaceae). It is one of the results of the Polypodiaceae-project that is being carried out under the supervision of Prof. Dr. Hennipman (State University, Utrecht). With this treatment of Pyrrosia, the group of the Platycerioid ferns (sometimes regarded as a subfamily) will be completed. The total number of genera in this group is reduced to two: Platycerium and Pyrrosia. Other publications dealing with this group are Hennipman & Roos (1982), dealing with Platycerium; and Ravensberg & Hennipman (1986), dealing with the former genera Drymoglossum and Saxiglossum, now in Pyrrosia. Together with Hennipman & Ravensberg’s account this forms the first complete account of Pyrrosia. The genus has been subject to revision on a world-wide scale only once before (Giesenhagen, 1901). In that work, however, several species were omitted and the genera Drymoglossum and Saxiglossum were not included. After Giesenhagen’s monograph, Pyrrosia has been the subject of several regional studies, most notably Ching’s (1935), which deals with the species from the mainland of Asia including Japan and Taiwan. The African species were revised by Schelpe (1952), the Australian ones by Tindale (1961). Nayar & Chandra’s (1965) account of the species from India emphasizes the morphology rather than the taxonomy of the species treated.