The process of drying parallelepipedic samples of wood is studied, by considering 3-dimensional transport of water along the 3 principal axes of diffusion, as well as evaporation out of the surface. During a large part of the process, the water content is considerably higher than the value associated with the fiber saturation point. A numerical model with finite differences, based on the assumption that the transport of water is controlled by transient diffusion through the sample and evaporation from the surface, is successfully tested with a beam in the following two cases : the initial concentration of water is uniform, or not. The model is capable of predicting not only the kinetics of drying, but also the profiles of concentration developed through the samples at various times. The principal diffusivities are determined by using a short test technique in transient condition.