In the vital observations of ascites cells by means of tissue culture conducted on 30 cases of tumor ascites, the author obtained the following results: 1. The average cell count is 642.5/m㎥. 2. The characteristics of the cell compestition are the appearance of tumor cells and tumorous signet-ring cells, a slight increase in the number of serous cells, a moderate increase of neutrophils, and the appearance of phagocytic signet-ring cells. 3. The detection of tumor cells and tumorous signet-ring cells is considered as the direct sign and the other cytological characteristics are considered as the indirect sign. 4. When the case showing less than six per cent of tumor cells is designated as group I, that over 20 par cent as group II, and hepatic cancer ascites as group III, each group presents respectively characteristic physio-chemical traits. 5. By vital observation tumorous signet-ring cells can be clearly distinguished from phagocytic signet-ring cells. 6. Cytological characteristics of different kinds of tumor cells, namely, adenoma, simple cancer, scirrhous cancer, colloid cancer, liver cancer, and coelothelioma cells, can be grasped by vital observation. 7. It has been possible to grasp the peculiarities of the cell-composition of ascites and cytological characterisitics of component cells as indirect sign, especially the characteristics differentiating tumor ascites from the ascites of liver cirrhosis.