Abstract: The dielectric constants and loss tangents of wood of 16 tree species in the radio frequency region have been measured. Results for the three species,Paulownia fortunei Hemsl.,Picea jezoensis Carr.and Betula albo-sinensis Burk.are presented in some detail.At low moisture content (below 3%),in these species the dielectric constants vary slowly and the maximum values of the various loss tangents occur with the frequency.The curves of 1gσ—1g for the above species are presented as straight lines.The relationship of all specimens between the dielectric constant and density based on the dry wood is in agreement with the Clausius-Mosotti relation.The dielectric values increase with increasing of the moisture content.The dielectric values are the highest in the longitudinal direction,and in the other two directions they are approximately the same.