A classification of the Neotropical bamboo genus Chusquea into five sections is proposed, and detailed descriptions of 32 of the ca. 120 species are presented. Shrubby, high-altitude species with intravaginal branching, formerly segregated as the genus Swallenochloa, are incorporated into Chusquea as section Swallenochloa (16 species). Three other smaller groups known from lower elevations are formally classified as section Verticillatae (six species), section Serpentes (five species), and section Longifoliae (five species). These four sections are well-defined, primarily on morphology of the buds, branches, and foliage leaves. The remaining species are provisionally assigned to section Chusquea. Morphological evidence supporting this classification is presented, and additional comments on chromosome numbers, phenology, habitats, and distributions are included. Two keys to species are provided, one based solely on vegetative characters and the other on vegetative and flowering characters. One new species, C. glauca, is described. The distribution of each species is mapped, and most species are illustrated.