Cytologic studies on vaginal smears have been carried on by many investigators for a quite long time and there are already numerous excellent results available. However, ever since the report on the diagnostic method for uterine cancers by Papeniceaou in collaboration with Traut in 1953 recomfirmatiom and re-investigation with vaginal smears have gained a new impetus in various fields as an important diagnostic method for malignant tumors. Especially in the field of gynecology it has been verified that this method is an important supplementary method for the diagnosis of uterine cancers, offering as it does a fairly accurate diagnosis in view point of a possibility of detecting clinically obscure cancers at an early stage. Likewise we have been endeavoring to detect uterine cancers at an early stage by giving screening tests of vaginal smears obtained at the first examination of all the patients visiting our clinic since August, 1957. Besides uterine cancers, there are also many studies on the vaginal smears in inflammation of sexual organs as well as in the field of the endocrinology. The author also carried out cytologic study on the vaginal smears in benign cases just as in malignant. Namely, the vaginal smears were taken from all the patients visiting our clinic from the beginning of August, 1957 to the end of December, 1958 and microscopic examinations were conducted after Papanicolaou's original method of staining. The results of the examiations were represented by types I, II, IIA, II+, III, IV, and V according to Carter's classification. Furthermore, the specimens obtained from gynecologic patients for the purpose of the screening test were divided into 10 classes according to the diagnosis given at the outpatient clinic, and these were further divided into three grades of those under 40 years, those between 41 to 55 years, and those over 56 years. Taking into consideration the possible cyclic changes because of the smears being taken only once at random, observations were carried out by selecting the samples under the same cyclic condition. By dividing the cells exfoliated in the vagina into five classes of deep cells, sub-basal, intermediate layer cells, superficial layer cells, and cornified cells and as the components other than those of epithelium, into leucocytes, erythrocytes, cervical canal cells, endometnial cells, and histiocytes. The cornification and acidophilic indices were determined. Of the total of 5, 456 cases 472 were diagnosed as positive or possibly-positive by vagnial smears, and 215 cases of the latter were biopsized and 184 of them were revealed to be carcinoma. Those proved to be negative by the vagnial smear test amounted to 4, 948 cases, 457 cases 22 revealed the carcinomatous changes in their biopsy specimens. When the percent age of accuracy by the vaginal smears is calculated, taking the biosy examination as the final criteria, the following results are obtained. Namely, 206 cases were diagnosed as squamous cell carcinoma intraepithelial carcinoma or adenocarcinoma by biopsy. Of them 184 cases were diagnosed as positive or possibly-positive by vaginal smears, and 466 cases were revealed to have no cancer by biopsy, and of the latter 457 were negative to the vaginal smear tests. Therefore, the positive percentage is 89.3 per cent, while the negative percentage is 98.1 per cent, bringing the rate of accuracy to 93.7 per cent. Those diagnosed as uterine cancer by vaginal smears and confirmed by biopsy amounted to 206 cases, 3.7 per cent of the total. In addition, 32 cases of blinically obscure cancers amounting 3.7 per cent of the total were discovered, proving that this technique is a useful supplementary method of diagnosis for dircovering uterine cancers in an early stage. Furthemore, in the cervical cancer of the uterus both basal and para basal cells can be observed numerously apart from cancer cells, and also leucocytes and erythroeytes can be observed in all cases.