The neotropical genusOchthocosmus is centered in the Guayana Highland of southern Venezuela. The taxonomic history, morphology, ecology, and geographical distribution are discussed in relation to the taxonomy of the genus. A key to the six species and four varieties, distribution maps, descriptions, and specimen citations are given. Two new species and two new varieties are described,O. longipediellatus Steyermark & Luteyn,O. attenuatus Steyermark & Luteyn,O. multiflorus var.angustifolius Steyermark & Luteyn,O. miiltiflorus var.canaripoensis Steyermark & Luteyn; and two new combinations,O. roraimae var.parvifolius (Hallier f.) Steyermark & Luteyn,O. roraimae var.grandifolius (Steyermark) Steyermark & Luteyn, are made.