The diffusion of methyl bromide into pine wood was examined in an exsiccator. In small specimens, longitudinal diffusion is much stronger than radial diffusion. In long boards, however, longitudinal diffusion was observed to stop about 70 cm from the end. In such cases, one can only rely upon radial diffusion, which is about equal in heartwood and sapwood, whereas longitudinal diffusion is considerably smaller in heartwood. Examples are given for the calculation of the methyl bromide quantity obtained in timber. -- AATA