The aim of the work was to evaluate in vivo the possible enhancement of efficacy of antitumor vaccine prepared on the base of cytotoxic lectine from B. subtilis B-7025 by its combination with probiotic mixture of Enterococcus faecium K-50 and Saccharomyces cerevisiae 14K or their metabolic products. MATERIALS AND METHODS: Experiments were carried out on the models of solid sarcoma 37 (S37) and metastatic Lewis lung carcinoma (3LL). Efficacy of treatment was evaluated by parameters of tumor growth, median survival time of experimental animals and volume of metastases. RESULTS: We have shown that combined application of antitumor vaccine with pro-and/or prebiotic resulted in synergistic effect in the therapy S37-bearing mice, whilst in 3LL-bearing animals application of vaccine along with prebiotic inhibited metastasis by 2-2.5-fold compared to animals treated by vaccine only. CONCLUSION: Application of pre- and probiotics (E. faecium K-50 and S. cerevisiae) markedly elevates efficacy of antitumor vaccine in vivo.