The transcriptional activities of the nuclei of the liver and spleen cells of rats were studied at the 1st, 4th, 18th, and 24th hour after whole-body irradiation with gamma rays. It was found that the transcriptional activity of the nuclei of rat spleen was invariably markedly suppresed in all the periods after irradiation while that of the rat liver demonstrated a diphasic change, that is, an exaggeration of the activity at the 4 th hour but a reduction at the 18th and 24th hour after irradiaiton. The change of the activity of RNA polymerase Ⅱ showed no difference from that of RNA polymerases Ⅰ+Ⅲ. The mechanism of these changes was briefely discussed.