The genus Aspidosperma is one of the basalmost genera in the Apocynaceae s.l. and are particularly dominant over much of Meso- and South America. Most closely related are Geissospermum and Microplumeria, both Neotropical genera, which differ mostly in fruiting characteristics. Perhaps the most unusual species, A.quebracho-blanco, appears to be closely related to the A.polyneuron group. A.cuspa, traditionally thought to belong to the A.polyneuron group, distorts the congruence between the morphological and molecular hypothesized relationships by taking a strong sister position to the A.myristicifolium and A.darienense clade. Another deviation from traditional taxonomic thought is the distinctness of the A.megalocarpon and A.illustre from the rest of the genus; our results suggest that these species are most closely related to the A.excelsum group which is intermediate in derivation. One of the confounding factors in Aspidosperma taxonomic progress and understanding is the inordinate amount of vegetative and, to a certain extent, floral plasticity exhibited by individual trees, particularly prevalent in the A.spruceanum group. Although parts of the Aspidosperma taxonomic puzzle remain unclear, the general framework of relationships is increasingly coming into focus.

Key words: Apocynaceae, Aspidosperma, Geissospermum, Microplumeria, molecular, relationships