The polymerization of acrylamide in aqueous solution was carried out with β-irradiation facilities using unsealed ⁸⁵Kr gas as an internal radiation source. Irradiation experiments were made in a reaction vessel of 1 l capacity with 290 Ci of ⁸⁵Kr. The effects of dose rate, monomer concentration, and polymerization temperature on the polymerization rate were studied. The experimental results were compared with the results using ¹³¹Cs as a source. It is observed that the polymerization rate, for either source, is proportional to the 0.55th power of dose rate and the 1st power of monomer concentration. In addition, the activation energy of polymerization is 1.8kcal/mol. It can be considered that there is no particular distinction in the polymerization rates due to difference in the radiation source.