Presents a full monograph of the Euphorbiaceous genus Aporosa. Aporosa consists of 82 species of small dioecious trees and is one of the more common genera in the tropical rain forests of Southeast Asia. The study first treats general aspects of the genus, e.g. a description of the macromorphological characters, a summary of some micromorphological features, notes on the ecology of Aporosa, and a compilation of uses mentioned for the various species. Hereafter phylogenetic relationships for the various taxa are proposed based on a consensus pattern, reconstructed using subanalyses, testing and consensus techniques. In this it shows an excellent example of how a species-rich group with much homoplasy can be partitioned and combined to get useful patterns.