Immune functions of mice bearing Lewis Lung Carcinoma (LLC) were significantly suppressed when evaluated with mitogen responsiveness, IL-2 production and non-specific suppressor activity. Based on these immunosuppressive characteristics of LLC bearing mice, immunomodulating activates of Copolang were investigated in this model. After 15 days of LLC inoculation, Copolang was intraperitoneally administered for 7 consecutive days with doses of 20 or 200 mg/kg. Immune functions were evaluated 3 days after the final administration of Copolang. The results showed that the growth of LLC solid tumor was not inhibited by Copolang. But, mitogens-induced proliferation, IL-2 production and responsiveness to recombinant IL-2 of splenocytes were significantly augmented by the treatment of Copolang. However suppressor cell activity was not affected by Copolang. These results indicate that Copolang expresses potent immunomodulating activates through the augmentations of IL-2 production and responsiveness to recombinant IL-2, which have been generally known to be suppressed in tumor bearing mice, without affecting the growth of tumor.