A resorcinol-formaldehyde resin (Elmer's Waterproof Glue) was tagged by the addition of 4% by weight of Meta-bromophenol. Tagging success was determined from S5NMR spectral analysis. Samples were sectioned in a microtome, weighed and irradiated in a nuclear reactor. The concentration in ppm of isotopic Bromine in each section was determined by neutron activation analysis and a profile representing the resin concentration gradient in and on the wood was obtained. Greater penetration either in terms of depth or often in terms of concentration increases the fracture toughness of the gluebond formed on the substrates tested. For procedure see: White, M.S. 1975. The influence of Resin Penetration on the fracture toughness of wood adhesive bonds. Ph.D. dissertation, Virginia Polytechnic Inst. and State Univ. Blacksburg, Va. -- AATA