The Buddlejaceae are a small family comprising eight genera and 125 species, approximately half of which inhabit the New World. Many species of Buddlejaceae are shrubs which inhabit xeric or subxeric habitats. The tree species are montane, growing primarily at 2000-4000m. More than a dozen species of Buddleja are cultivated, and widespread sources indicate that species of this genus have been used for centuries in the New World for a variety of ills. In this monograph, 27 species of Buddleja, (inlcuding 4 adventive Old World taxa), 2 species of Emorya, and the more remotely related monotypic genera, Polypremum and Peltanthera, are treated. The genus Sanango has recently been reclassified in the Gesneriaceae. Includes keys, descriptions, distribution maps, black and white illustrations, and photographic images.