The degree of conversion of the monomer diallyldimethylammonium chloride (DADMAC) to its polymer, poly(DADMAC), was determined using dynamic thermogravimetry (TG). DADMAC solution was exposed to different radiation doses, and the degree of conversion of the monomer to the polymer was determined from a calibration plot generated previously from solutions containing known monomer–polymer ratios. The concentration of monomer and polymer in the mixture was estimated by measuring the weight loss corresponding to the steps involved in the thermograms. By employing the method, polymerization of DADMAC as a function of irradiation dose was studied. The degree of conversion of DADMAC increases considerably during the initial stages of irradiation, up to a dose of 40 kGy, after which the increase in conversion is not very significant. To validate the method, the degree of conversion was also determined by classical gravimetry, and the results were found to be in good agreement..