Coniferous timber in the Douglas-Fir Region is commonly subject to attack by ambrosia beetles of the families Scolytidae and Platypodidae. In view of the variety and extent of damage there is need for a ready method of identifying the ambrosia beetles causing major losses. It is the purpose of this paper to present methods of identifying the genera of ambrosia beetles found in the Douglas-Fir Region, by the general body shape of the insect, the diameter of the tunnel the beetles bore and the shape of the wood borings which they eject from these tunnels. These methods were developed by the author from original work conducted at Corvallis, Oregon in 1955-56 as part of his master's thesis at Oregon State College. Kinghorn, in Canada, developed similar methods of distinguishing ambrosia beetle damage and recently published means of differentiating the work of Gnathotrichus, from Trypodendron (Kinghorn, 1957).