Surfaces of wood disks were continuously exposed to 16 mg/l of methyl bromide (MB) or sulfuryl fluoride (SF). Fumigant diffusion through 25.5 mm of softwood or 19.5 mm of hardwood was determined by gas chromatography. Fumigant concentrations attained equilibrium levels in less than 3 hrs through transverse surfaces of pine. Tangential/radial surfaces of pine, western hemlock, and Douglas-fir were, in increasing order, more refractive to diffusion of both fumigants. Hydration of pine disks reduced SF diffusion proportionally more than MB, while paint on surfaces of pine and mahogany decreased MB diffusion proportionally more than SF. With the exception of hydrated wood, significantly more SF diffused through test matrices than MB in all 20 hr and most 3 hr determinations. Fumigant diffusion to target sites in wood was conducted under worst case assumptions. Under actual conditions, fumigant diffusion would be greatly enhanced by the gallery structure of common wood-infesting insects.PSUBKY=methyl;bromide;sulfuryl;fluoride;structural;fumigation;wood;diffusion