Some studies have indicated that boosting the immune response of the organism with cytokines (GM-CSF, IL-2, IL-12, TNF-α) can increase the response rate of the tumors to electrochemotherapy.8–14,16–18,62 In our study, we have observed that the intramuscular mIL-12 gene electrotransfer successfully increases the response rate of the tumors by approximately 20% tumor cures, both in the immunogenic sarcoma and moderately immunogenic carcinoma models. The gene discussed is TNF; the disease is neoplasm.