The studies were conducted to investigate the combined effects of Tonics and Mitomycin C(MMC). The effects of Tonics and MMC on the proliferation of Molt-4 cells, human leukemic cell line, and activation of human lymphocytes were estimated by MTT colorimetric assays. Selected medicines among 9 kinds of Tonics by results of MTT assays were treated with MMC in mice. The Tonics itself enhanced the proliferation of Molt-4, but the anti-proliferative effect of MMC was not intercalated by the combined treatment of Tonic and MMC. Inhibitory action of MMC was augmented by Sa Kun Ja Tang(SKT). This result was due to the inhibition of DNA synthesis. Among 9 kinds of Tonics, Sip Jean Dae Bo Tang(SDT), Saeng Maek San(SMS) and Kwi Bi Tang(KBT) did not inhibit the action of MMC, but activated lymphocytes. When the mice were treated by MMC, the number of leukocytes was decreased significantly at the 1st day, but recovered at the 7th day. In the groups of MMC treated with SDT or KBT, the number of leukocytes was increased significantly than the group of MMC treated only at the 3rd day. Combined treatment of the Tonics(SDT, SMS) and MMC retained the body weight of mice at the level of normal mice. SDT, SMS and KBT did not change the number of plaque forming cells(PFC), but MMC treated group decreased the number of PFC. The combined treatment of MMC and SDT increased the number of PFC significantly than the MMC treated group. SDT, SMS and KBT did not influence the proliferation of T cells, but MMC treated group decreased the proliferation of T cells. The combined treatment of MMC and those tonics increased the T cell proliferation significantly than the MMC treated group. In conclusion, the results presented in this paper suggest that SDT, SMS and KBT can recover the side effects of MMC, such as weight loss, leukopenia and immunosuppresion, without any intercalating the anti-proliferative action of MMC in vivo.