The therapeutic efficacy of the preoperative administration of DTIC and its benzenoid analog DM-COOK, in terms of prolongation of the life-span of mice bearing Lewis lung carcinoma lines with different metastatic potential, has been evaluated in combined experiments with surgery and postsurgical non-specific immunotherapy with the peptidoglycan monomer PGM. The effects of the presurgical selective antimetastatic treatment with the dimethyltriazenes consist of a statistically significant prolongation of the survival time of the treated mice. The activity is more pronounced, in terms of animals cured, using the tumor line which is endowed of a low ability to colonize the lungs. The addition of postsurgical immunotherapy with PGM improves the overall therapeutic efficacy of the combined treatment with triazenes and surgery, independently from the tumor line used. In general, the presurgical treatment with the benzenoid triazene DM-COOK, causes antineoplastic effects slightly better than those observed using the imidazole derivative DTIC.