Preoperative roentgen-irradiation (unilaterally 1-12 times) treatment was given to 216 cases with cervical carcinoma, and 24 hours after the completion of irradiation Okabayashi's radical extensive hysterectomy was performed. The author studied the irradiation susceptibility of metastased cancer cells by comparing the original site of cancer with metastased lesions and the metastatic irradiated side with non-irradiated side, with a special emphasis on the mitosis of cancer cells. As for the significance between C.P.L. type (Imai) of the primary cancer and the metastatic foci, the change in the mitotic picture due to roentgen irradiation in C-type metastatic foci is significantly greater than that in L-type metastatic foci; and therefore, the irradiation susceptibility in C-type can be said higher. Namely, in this instance the irradaation susceptibility and the prognosis have the same tendency. As for the relationship between Nagase's classification (Types Ⅰ, Ⅱ, Ⅲ) of the primary cancer and its metastatic foci, the change in mitotic picture due to roentgen irradiation in the case of Type Ⅱ metastatic focus is greater than in Type Ⅰ metastatic focus, and the irradiation susceptibility in Type Ⅱ tends to be higher. In other words, in this instance the irradiation susceptibility is in no way associated with the prognosis. Therefore, it is dangerous to deduce the prognosis from the irradiation susceptibility of cancer cells. Numbers of giant cells appearing due to irradiation increase in proportion to the degree of the destruction of the cancer focus irradiated upon. Therefore, in the observation of dividing cells in the irradiated cancer focus, it is essential to pay attention not only to the change in the number of cells but also to the variety of the degeneration picture. The degree of degeneration in dividing cells increases in propoetion to the irradiation amount, and by a irradiation more than 1,300 r (deep dosis) the mitotic picture changes markedly, thus bringing about the cell disintegration. On applying an irradiation tube on the anterior surface, its lower margin is placed just above the pubic symphysis, and its inner margin is about 2 cm. outside the medial line; and on applying it on the posterior or lateral side, its lower margin is placed on both greater trochanters; and from the posterior side it is irradiated at the angle 20℃ to the side of the head. In other words, it is believed that main lymph nodes in the pelvis are almost all equally irradiated by irradiation at the sites mentioned above.