Tropical plants show a diversity of growth forms, yet few phylogenies are available to examine the transitions between trees, shrubs, and lianas. Here, we reconstruct relationships among 37 species of Ayenia, Byttneria, and Rayleya with cpDNA sequences, and use the resulting phylogeny to test hypotheses on the evolution of climbing plants and to examine biogeography of these plants. Results show that Rayleya is sister to a combined clade of Ayenia and Byttneria; Byttneria is paraphyletic with Ayenia nested within it. The common ancestor of the combined Ayenia/Byttneria/Rayleya clade is reconstructed as a neotropical tree or shrub. Within the Ayenia/Byttneria clade, there is a single transition to unarmed lianas, with subsequent radiations into the Asian and African tropics. A second independent transition from trees or shrubs to spiny, semi-scandent shrubs occurred in the neotropics. We found no evidence of transitions from lianas to any other growth form; however, we recovered a reversal from semi-scandent shrubs to fully upright plants. Within the neotropics, there are two independent radiations into seasonal, open habitats. Additional sampling of African species of Byttneria may yield more complicated scenarios in both biogeography and the evolution of growth forms.