1-131-Lipiodol a new therapeutic agent has been used in the treatment of hepatocellular carcinoma (HCC) sine Lipiodol retains within the vascular HCC following intrahepaitc arterial injection. Radioiodination of Lipiodol wasachieved by using a simple exchange method and the agent was used for the treatment of HCC following the biodistribution studies in dogs and human subjects. Desired radiation doses can easily be delivered upto 12000 rad while keeping the radiation doses to nor-mal liver lung and whole body safe and tolerable. Clinical studies in 50 patients with hepatoma were perform-ed by this method in order to estimate the therapeutic effect sagety indication and limitations. The results as follows: 1. Biodistribution studies The effective half life of 1-131 -Lipiodol in the tumor was 6 days and retained in the tumor as long as 3 months. About 10% of radioactivity was demonstrated in the lung with effective half life decay. The 1-131-Lipiodol in the normal liver tissue seems to be metabolized in the hepatocytes and excreted into the bile and urine. No demonstrable radioactvity was noted in the thyroid bowels spleen and bone marrow. 2. Histologic studies. Histologic studies following the intrahepatic 1-131-Lipiodol of the canine liver revealed the Lipiodol par-ticles in the bile duct cells and cytoplasm of hepatocytes. In human resected hepatomas after 1-131-Lipiodol infusion Lipiodol drophlets were demonstrated in the tumor vessels sinusoids as well as in the tumor cell cytoplasm. Extensive hemorrhagic necrosis of trmor was demonstrated after treatment with 1-131-Lipiodol. 3. Clinical studies Response rate was most prominent in those cases of single massive types which measures less than 5cm in diameter. Multinodular type was also responsive rather than single massive type however infiltrative type of tumor or the tumors measuring more than 8cm was less effective on this therapy. 4. Adverse reactions Adverse reactions from the procedure include fever abdominal pain and elevation of liver function which were mild and tolerated well. There were no side effects suggestive of bone marrow depression or lung com-plications. In conclusion 1-131-Lipiodol is a promising agent for the treatment of hepatoma less than 8cm in size by simple or multiple procedures diverling high internal radiation dose to the tumor without any bone marrow depression lung complications or radiation hepatitis.