The swelling rates of wood in various vinyl monomers were measured. Loblolly pine (Pinus taeda, L.) wafers were soaked in methyl methacrylate (MMA), styrene (ST), acrylonitrile (ACN), ethyl acrylate (EA), and binary mixtures of ST-ACN and EA-ACN. The M.C. of the wood had a dominant effect on dimensional change. At high M.C. (15%) the wood was dehydrated by the monomer and shrank. At low M.C. (5%) the wood swelled. From studies with dry wood and dry monomer it was concluded that part of this swelling was due to the wood removing water from the monomer and part was caused by the monomer itself. The ST-ACN mixture had a very high swelling rate and equilibrium swelling value. This was found to be virtually all due to the ACN component in the mixture. -- AATA