Infection of CDF1 mice with non-toxic doses of different strains of mycobacteria had no influence on the growth rate of the L1210 leukemia. In combined therapy, pretreatment of mice with M. smegmatis did not show any significant effect on the antitumor activity of adriamycin when tested in mice inoculated iv with 10(3) leukemic cells. Moreover, for high doses of adriamycin (15, 20 mg/kg) combined with post-treatment with mycobacteria the shortened survival time was observed. In experiments in which mice were injected iv with 10(2) L1210 cells potentiation of antileukemic activity of adriamycin in infected animals was achieved.