AIM: To investigate the effect of astragaloside IV (ASI) on T, B lymphocyte proliferation, antibody production, and cytokines produced by murine peritoneal macrophages. METHODS: MTT assay was used to determine T, B lymphocyte proliferation and quantitative hemolysin spectrophotometry (QHS) assay was applied to test antibody production; IL-1 production was measured by thymocyte proliferation assay; TNF-alpha production was determined by the cytotoxicity assay against L929 cells. RESULTS: 1) In vivo, ASI 50 - 200 mg/kg ig for 7 d increased T lymphocyte proliferation and antibody production, and ASI 50 - 100 mg/kg ig for 7 d increased B lymphocyte proliferation but ASI 200 mg/kg had no effect on B lymphocyte proliferation; 2) In vitro, ASI increased T, B lymphocyte proliferation only at 100 nmol/L; 3) ASI increased IL-1 activity at I nmol/L in vitro, but decreased it at 100 and 1000 nmol/L; 4) ASI inhibited TNF-alpha activity with or without LPS-stimulation in vitro. CONCLUSION: ASI increased T, B lymphocyte proliferation and antibody production in vivo and in vitro; but inhibited productions of IL-1 and TNF-alpha from peritoneal macrophages in vitro.