Radiation initiated in-source polymerisation of trioxane has been studied in super dry state. The dose rate exponent observed is 0.51 indicating the termination to be bimolecular i.e. neutralisation of cation with an anion or an electron. From the molecular weight data the rate constantsktr/kpandkt/k2phave been evaluated to be 2.5 × 10−4and 13 respectively. Thektris the rate constant for the chain transfer to the monomer andkpandktare the rate constants for propagation and termination all expressed in M−1s−1. Assuming the neutralisation between the ions andktvalue of isobutyl vinylether taken from the literature, thekpvalue was calculated to be 1.6 × 105. TheG(total ions)was calculated to be equal to 9.1.