By conducting a histological study on the parametrial tissues of the cervical carcinoma in 237 patients previously irradiated with a small dose of X-ray, the author investigated the radiosensibility of the parametium with special references to the relationship between the changes in mitotic picture and giant cells on one hand and the C.P.L. and Nagase's classifications on the other. Those receiving 1-12 x 300 r were 215 cases and they were divided into 2 groups of 6 or 12 times; and also the deep dosis of X-ray was estimated. By obtaining the tissues of cervical carcinoma after hysterectomy, tissue specimens were prepared by Hamazaki's sublimate fixation and stained in a 1.0% Bomer's hematoxylin solution. The following are the results of the present study. 1. The cancer infiltration in the parametrial tissues has been found in 27.8 per cent of the cases studied, and this proves on the left side to be one and half times as great as that on the right side tissues. Moreover, this infiltration is contiguous with the regions adjacent to the cervix and is situated mostly near the uterine arteries. And the cancer infiltration in the parametrial tissues in the C.P.L. classification revealed type L twice as many as type C, and the same in Nagase's classification showed more of types Ⅱ and Ⅲ (particularly type Ⅱ) than type Ⅰ. 2. The changes of the cancer tissues in the parametrial tissues after X-ray irradiation as well as of Feulgen reaction are directly proportional to the amount of X-ray irradiated. 3. The changes in mitosis, atypical cell-division and giant cell appearance clearly paralleled with the amount of X-ray employed. Mitoses decrease after 1-4 times of irradiation, and are arrested thereafter. The atypical cell division increases sensitively after 1-3 times of irradiation, while giant cells increase rapidly after 12 times of irradiation. 4. Relative to the C.P.L. classification, in the cases given 6 irradiations giant cells increase in type L, but in the cases with 12 irradiations mitoses decrease, and in the cases showing an increase in atypical cell division changes due to X-ray are strong in type C. 5. With respect to Nagase's classification in the cases given six times of irradiation the changes due to X-ray are marked in type Ⅰ with a decrease in mitoses and type Ⅱ with an increase in giant cells, while in the casese irradiated 12 times the changes are striking in type Ⅰ with an increase in giant cells. In other words, proportionately with the increase in the amount of X-ray, the changes in connective tissues become greater in type C and type Ⅰ. 6. Considering various atypical cell divisions according to the shape of each cell such a cell division increases well proportionately to the amount of X-ray irradiated in respective case, but by 12 irradiations (especially in type C) cells are condensed at first and then the atypical cell division increases at the terminal stage.