The four kinds of anti-tumor agents i. e. endoxan (0.5 mg per mouse, three times), nicotinamide (15 mg per mouse, three times), DPN (40 mg per mouse, one time) and colchicine (4 mg per mouse, one time) were subcutaneously administered to dds-mice which had been transplanted with Ehrlich ascites tumor seven days previously. And the changes of the activity of the DPN diaphorase, TPN diaphorase, succinic degydrogenase (SD) and α-glycerophosphate degydrogenase (α-GD) of the ascites tumor cells were cytochemically examined in the smear method and suspension method. 1) In general, their was no definite morphological change of the cells except for inhibition of mitosis in the above dosages, nor destruction of the enzymes. But a few variations of the enzymatic activity were noted. 2) After the administration of endoxan, stainabilities of the DPN diaphorase, SD and α-GD were slightly increased, while that of the TPN diaphorase showed no change. 3) After the administration of nicotinamide, the number of tumor cells with the high activity of the DPN diaphorase and TPN diaphorase was increased about five per-cent. NO change of the activity of the SD and α-GD was observed. 4) After the administration of DPN, the number of tumor cells with the high activity of the DPN diaphorase was increased about ten per-cent. But no change of the TPN diaphorase, SD and α-GD was observed. 5) After the administration of colchicine, there was no change of the activity of the DPN diaphorase, TPN diaphorase, α-GD, while the SD activity was increased in lesser degree.