The four kinds of anti-tumor agents i.e. nitromin (0.5 mg per mouse, four times), colchicine (0.05 mg per mouse, one time), sakomycin (5 mg per mouse, one time) and mitomycin C (0.04 mg per mouse, one time) were intraperitoneally administered to dds-mice which had been transplanted with Ehrlich ascites tumor seven days previously. And the changes of the DPN diaphorase, TPN diaphorase, succinic dehydrogenase (SD) and α-glycero-phosphate dehydrogenase (αGD) of the ascites tumor cells were cytochemically examined in the smear method and suspension method. 1) In general, moderate morphological changes of the tumor cells by these anti-tumor agents were observed, and the changes of the stainability of the oxidative enzymes were often observed. 2) After nitromin administration. no change of the stainability of the DPN diaphorase and TPN diaphorase in the smear method and slight increase of their stainability in the suspension method were observed. The stainabilities of the SD and α-GD were decreased in lesser degree in both methods. 3) After colchicine administration, no change of the stainability of the DPN diaphorase and TPN diaphorase in the smear method was observed, but their stainability of all tumor cells showed a tendency down to keep same intensity. A slight decrease of the stainability of the SD and α-GD was observed in the smear method, while their stainabilities were slightly increased in the suspension method. 4) After sarkomycin administration, stainabilities of all four enzymes were decreased in certain degree in the smear method, but the DPN diaphorase and TPN diaphorase staining intensity were remarkably decreased in the suspention method and their stainabilities of all cells showed a tendency down to keep same intensity. The SD and α-GD staining intensity were also decreased slightly in the suspension method. 5) After the administration of mitomycin C, changes of the staining intensity of the DPN diaphorase and TPN diaphorase were scarcely observed in both methods. The staining intensity of the cells in the end stage of the interphase showed to be decreased in lesser degree. Stainabilities of the SD and α-GD were slightly decreased in the smear method, while their stainabilities were slightly increased in the suspension method. 6) It might be assumed that the decrease of the stainability reacted with the anti-tumor agents in the smear method specimen showed decrease or destruction of the oxidative enzymes and that the change of stainability reacted in the suspension method specimen showed change of the activity of the enzymes.