Chan Khao is a local name of wood crude drugs, which possesses antipyretic activity in Thai traditional medicine. It is used in several recipes in the National List of Essential Medicine of Thailand. From Thai traditional textbooks, the sources of the crude drug may be three species, i.e. Diospyros decandra Lour., Santalum album L., and Tarenna hoaensis Pit. The macroscopic characters of Chan Khao wood crude drug are similar but an identification tool for the source of Chan Khao crude drugs is lacking. Wood anatomy of the sources of Chan Khao crude drug was investigated to reveal the microscopic characters for constructing the identification keys. The wood anatomical study was performed by using sliding microtome with three sectional views, i.e. transverse, radial and tangential views. The result showed that the transverse section of D.decandra presented the pattern of vessel arrangement in radial multiple andband axial parenchyma in one-celled wide. While the vessel arrangement of both S.album and T. hoaensis showed solitary pattern. The axial parenchyma of S. album was diffuse-in-aggregate and T. hoaensis was sparsely diffuse in small number. For the longitudinal radial plane, the remarkable feature of T. hoaensis was disjunctive ray cell. The prismatic crystalswere found in axial parenchyma of S. album, while D. decandra presented the numerous crystals in ray cells. According to the longitudinal tangential plane, the seriate Kribs ray types were useful to distinguish the three different Chan Khao species. Heterogeneous types I, IIA, and IIB were found in T.hoaensis, D. decandra and S. album, respectively. The identifi cation key based on anatomical wood characters was constructed.