AbstractGamma radiation induced polymerization of vinyl chloride (VC) and copolymerization of vinyl chloride (VC)‐vinyl acetate (VAc) in Taiwan cedars have been investigated at low temperatures. The polymerization‐rate of VC and the copolymerization‐rate of VC‐VAc system in wood were found to be proportional to the n powers of the dose‐rate, where n became close to the value of 1 as the polymerization temperature being lowered below 0°C. The oxygen in air was recognized to induce the delay of the induction period due to its retardation on the polymerization. The apparent activation energies of VC and VC‐VAc for the polymerization and the copolymerization in wood were determined by use of the Arrhenius plotting as 4.0 Kcal/mole and 3.4 Kcal/mole respectively at the temperature‐range of —15°C∼20°C. The degree of polymerization of VC was greatly affected by the polymerization temperature, although it was observed to be independent on the total gamma dose within 1 Mrad and the kinds of wood. No graft reaction of PVC polymer and PVC‐PVAc copolymer onto the wood cellulose was found, while low graft percentage of about 3% being obtained at 20°Cin the case of using swelling agents. However, this value was found to be decreased to 0.1% at the temperature of —15°C. Based on the above‐mentioned experimental results, the radiation induced low temperature polymerization of VC or copolymerization of VC‐VAc system in Taiwan produced cedars are considered to proceed with ra