１３１Ｉ was labeled on lipiodol molecule by an iodine exchange reaction. The labeling rate was 95%. No dehalogenation was detected within 15 days at room temperature or after slerilization. Animal experiments showed that after hepatic arteial injection, １３１Ｉ-lipiodol was selectively accumulated in the embolizated local area. No increased acti-vity was observed in thyroid, lung or other areas in the body. The blood radioactivity per ml was 0.09±0.04% of the injectd dose. The result suggest that １３１Ｉ-lipiodol is very stable and suitable for clinical application.