Since Broders and Martzlff's report on the relation of irradiation susceptibility of the cervical carcinoma with the prognosis, there appeared many studies on the same subject by various investigators. And with the recent reports on the C.P.L. classification and Nagase's classification it has become clearly established that there is a close relationship between the irradiation susceptibility and prognosis. In the present paper are presented the results of observations on histological changes, especially changes in the mitotic picture and the appearance of giant cells, in the tissue specimens prepared before and after irradiation from 205 operable cases with cervical carcinoma, who had been treated with irradiation (mainly bard roentgen and some by radium irradiation) and then operated on by Okabayashi's method during the periodfrom August 1956 to December 1957, and also presented are comparative studies of these results with the CPL classification and Nagase's classification. 1) The histological changes turn generally markedly with incresed amount of radiation, but the change observable in each individual case reveals a marked individualistic difference, yet showing not necessarily any parallelism in the histologicai change with the amount of radiation within the surface dosis of 3,600 r. 2) No specific relationship exists between the histological change and the C.P.L. classification or Nagase's classification. 3) As for the change in the mitotic picture, the normal mitosis is rapidly diminished by irradiation, finally disappearing completely with the increase in the amount of radiation, while on the contrary abnormal mitosis is markedly enhanced by irradiation. 4) As for the relationship between the change in the mitotic picture and the C.P.L. classification, in the case given six roentgen irradiations (surface dosis of 1,800 r.) there is no significant relationship, but in the cases given 12 rounds of irradiation (surface dosis of 3,600 r.) the change in Type C is greater than that in Type L. 5) As regrads the relationship between the chang in the mitotic picture and Nagase's classification, no specific relationship can be recgonized in the cases administered with 6 rounds of irradiation an increase in the appearance of abnormal mitosies in Type Ⅰ is more pronounced than that in Type Ⅱ or Type Ⅲ. 6) Giant cells appear increasingly after six rounds or more of irradiation; and in the cases given 12 rounds of irradiation they appear significantly more numerously in Type C according to the CPL classification while more significantly in Type Ⅰ according to Nagase's classification. The actions of irradiation on cancer tissue may be roughly divided into a direct action on cancer cells and an indirect action derived from the influences on the local interstitial tissues and on the systemic metabolism. However, it seems that the irradiadiation susceptivility first of all and subsequently the problem related the prognosis can be solved only when these direct and indirect actions are summarily studied.