Effectiveness of electrochemotherapy against colorectal carcinoma (CRC) was evaluated in a mouse model. When mice with a subcutaneously established CRC tumor were administered intratumorally, intravenously or intraperitoneally with bleomycin (BLM) ranging from 1/50 to 1/2 of the 50% lethal dose, significant suppression of tumor development and even some cures were observed. When various electric field intensities ranging from 500 to 2,000 V/cm were applied for electrochemotherapy with BLM, all treatment protocols were similarly effective. Furthermore, when electrochemotherapy with the lowest dose of BLM and the lowest electric field intensity was repeated, complete cures of CRC were achieved in all animals.