Objective: To study antagonistic effect of Angelica Sinests(Oliv. ) Diels Lactone (ASDL) on the immunosuppressive responseinduced by Cyclosporin A, Hydrocortisone and antitumor agents. Methods: Immunodeficient models were used in the experiments. Immunosup-pressive response was induced by immunosuppressive and antitumor agents. In the different concentration of ASDL, antagonistic experiments wereobserved in vivo and vitro. Results: ASDL (62.5, 125.0, 250.0 ug/ml) could completely antagothe the mild inhibition (less than 50% ) ofmurine mixed lymphocyte reaction (MLR) caused by Cyclosporin, Mitomycin C, 5-Fluorouracil, Cytarabine and partly antagonize the seriousinhibition (more than 50% ) induced by Hydrcortisone in vitro. ASDL <10 or 20 MG/(kg. d)× 7, i. p> could antagonize inhibition of immunologi-cal function caused by cyclophosphamide (CY,80 mg/kg, s. c), which could promote the declined T lymphocyte proliferation, restore the reduced NK Cell cytotoxicity and productipn of IL-2. Conclusion: ASDL could antagonize immunosuppressive response induced by chemical agents.