The protein and protein-bound amino-bases in the Ehrlich solid carcinoma and NF sarcoma were histochemically examined. And the influences of the antitumor agents, i.e. Colchicine, Nitromin, Sarcomycin, Mitomycin C, Endoxan and Merphyrin on these tissues were also observed, and the following results were obtained. 1. The stainability of the protein-bound SH and SH-SS was slightly increased by the administration of the antitumor agent. Both tumors showed moderate reaction in the proliferating area of tissue, while they showed always moderate or high reactions in the area of necrobiosis or degeneration, and especially remarkable by the administration of Mitomycin C and Sarcomycin. 2. The protein-bound SS reaction did not reveal so remarkable changes by antitumor agents in both tumors, but was moderately increased by Colchicine administration. 3. The tyrosine reaction did not show the definite regularities in both tumors by the administration of the antitumor agent. 4. The protein-bound NH(2) reaction did not show the definite regularities in both tumors by the administration of the antitumor agent. Especially, the reaction in the proliferating area of the NF sarcoma was moderately increased by the administration of Sarcomycin and Mitomycin C. 5. The phenol and its compounds reaction did not show the remarkable changes in both tumors by the administration of the antitumor agents.