Nylon 6 powder and film (IAF film) were iodinated with 0.2, 0.4, 0.6 and 1.0 N of 12/Kl aqueous solutions, and the lodinated powder was used to make the films iodinated before forming (IBF film) . The adsorption state of iodine In the two kinds of films was investigated through thermogravimetry and infra-red analysis. With increasing concentration of Ij/kl, weight gains of the nylon 6 film and powder increase markedly to 0.4 N and 0.2 N, respectively, but above that concentration the increasing tendencies for both films diminish. The TG curves of IAF film indicate three distinct zones which have been suggested by one of the authors et nt. Furthermore, the lowest temperature zone (zone I), corresponding to evaporation of molecular It, can be divided into two sub-zones: zone I-1 and I-2, corresponding to excess 12 and l2 decomposed from Isions, respectively. By results of quantitative analysis for each zone, the weight loss of zone I-2 corresponding to relative quantity of Is- ion Is very low for the case of 0.2 N and increased considerably above that concentration. TG curves of IBF film do not indicate the Bone I-1, which may result from the fact that all of the excess li in the iodinated powder have been evaporated atready. IR spectra show that the hydrogen bonds between nylon 6 molecules are weakened and/or destroyed and content of moisture is increased by iodination. These tendencies of IBF films are more remarkable than those of IAF films.