This Guide intends to make it as easy as possible for the interested non-specialist to identify every known tree species in the Brunei area (approx 2000). The principal tools are clear line drawings, which are provided for every species and clarify the keys; simple descriptions with the absolute minimum of technical terms, in which only basic descriptions and diagnostic characteristics are included; and keys which rely, almost entirely and to the full extent possible, on characters that can be discerned in the field in all seasons with a knife, a pair of binoculars of appropriate magnification and a hand lens-and also in the herbarium. A glossary at the end of this book contains simple definitions of all terms used, as well as technical terms often encountered in other botanical literature. Colour photographs of the habit, bole, flowers or fruit of representative species are also provided. This Guide is aimed at teachers and students, foresters and agriculturists, hikers and ecotourists, in fact every person who has an enthusiastic interest in trees.