There are two general types of insects which are important enemies of timber. Termites--dry wood, damp wood, and subterranean--belong to one type; the other type consists of various families of beetles belonging to the order Coleoptera, of which four families are of primary importance in the United States. These four families are the Anobiidae, (Furniture and Death-Watch beetles), Bostrichids (False or Large Powder-Post beetles), Lyctidae (True Powder-Post beetles), and the Cerambycidae (Longhorn beetles). The purpose of this article is to give information on the biology of these beetles and describe the damage done by representative members of these families of beetles. Information on methods of control with a discussion of the relative merits of each will also be given.