Danggui Buxue Tang (DBT) is prepared from Radix Astragali and Radix Angelicae Sinensis. This Chinese herbal decoction has been shown to stimulate the proliferation of T-lymphocytes; however, the action mechanism of this stimulation has not been revealed. In cultured T-lymphocytes, application of DBT markedly induced the cell proliferation, the release of interleukin-2, -6 and -10, as well as the phosphorylation of extracellular signal-regulated kinases (ERK). The pre-treatment of ERK inhibitor blocked the DBT-induced immune responses. In addition, the polysaccharide-enriched fraction of DBT showed marked responses on the cultured T-lymphocytes suggesting the important role of DBT polysaccharide in triggering such immune responses.