In this paper are presented the results of experiments conducted to see the influence of 5 different anticancer agents (Colsemid, Carcinophillin, Glucosamin, Nitromin and OX substance i.e. unsaturated fatty acid fraction extracted from the liver of rabbits given total body irradiation) on cellurlar morphology, activity and cell count of Yoshida sarcoma cells in cell-suspension culture. These are summarized as follows: 1. In the case with Colsemid (dose of 10 and 100r/ml, incubated for 12 hours): After 12 hours, granulation of mitochondria and an increase in the number of pair cells were observed. Cellular damages were greater with the dose of 10 than with 100γ. 2. In the case with Carcinophillin (dose of 50 and 100 units/ml, incubated for 12 and 24 hours): There was marked shrinkage of the cells; shrinkage of the nuclei, nucloles and cytoplasm, with an increase in the number of shrunken, degenerative granules. Despite such a high degree of cellular damages there was no significant decrease in the number of cells. It may have been due to the fact that the shrunken cells are hard to be destroyed. 3. In the case with Glncosamin (dose of 1 and 10 mg/ml, incubated for 24 hours): In the dose of 1 mg/ml of Glucosamin no marked damage of the tells was recongnized. However, with the dose of 10 mg/ml, 12 hours after incubation, the cells presented an entirely different picture as compared with the case of 1 mg/ml. The cells were filled with many round, solidlooking vacuoles, and the nucleus and mitochondria were barely visible among these vacuoles. After 24-hour of incubation, masses of vacuoles and degenerative granules completely replaced the cells. 4. In the case with Nitromin (dose of 100 and 500r/ml, incubated for 12 and 24 hours); After 12 hours, swelling of the cells was marked, and the general struture of the cells appeared indistinct. Some of the cells had non-motile, peculiar pseudopodla. A few so softlooking vacuoles were recognized. Mitochondria became granular and further they were transformed into small vacuoles. After 24 hours, only aggregations of large and small vacuoles were seen floating instead of live cells. 5. In the case with OX substance (dose of 0.1 and 0.4 ml/ml, incubated for 6, 24 and 48 hours): After 6 or 24 hours of incubation, there could be recognized shrinkage and disintegration of the nuclei and lipoid granules, or swelling and disintegration of the cell margin. These changes were quite similar to the simultaneous effects of Carcinophyllin and Nitromin upon the cells. In the case with 0.4 ml/ml of OX, after 24 hours of incubation, the cells were completely destroyed, and with 0.1 ml/ml of OX, after the same period of incubation afterwads, the majority of the cells were dead, leaving a few surving cells among the dead ones. In the case where the medium was supplemented with unsaturated fatty, acid fraction extracted from the liver of rabbits not irradiated with X-rays, the cell growth was greatly enhanced and from the viewpoint of cellular morphology and cell count, there could be obseved no injurious effects of this fraction on the cells.