Combining nodal anatomy, the pattern of vascular tissue in the petiole, and the accessory characters, it is possible to identify taxa on several levels. This is a particularly useful device in the determination of sterile material. Although anatomy alone is not sufficient for resolving phylogenetic problems, it may give an added dimension to taxonomic investigations. The following families of the Guttiferales are treated: Ochnaceae, Quiinaceae, Caryocaraceae, Marcgraviaceae, Theaceae, Guttiferae, and Hypericaceae. Sixty-severn genera and 137 species are recognized. The anatomical details of node and petiole are shown in a series of semidiagrammatic drawings. Petiole anatomy is discussed as a means of elucidating relationships within the Guttiferales and as a method of identification.