Angelica sinensis radix, Danggui, is a traditional oriental medication, which has been used to modulate immune response. We report here that aqueous extract of Angelica sinensis radix (ASR) can induces NO production, and inhibit LPS-induced NO production in dose-dependent manner in RAW 264.7 macrophage cells. ASR also induces iNOS mRNA and iNOS protein expression, and exhibit inhibitory effect on iNOS mRNA and protein expression in a dose-dependent manner in LPS-stimulated RAW 264.7 macrophage cells. Cytokines involved in the regulation of inflammatory reaction and immune response may play a role in the pathogenesis. ASR induces. pro-inflammatory cytokine gene expression (IL-1α, IL-1β and IL-6 gene) in a dose-dependent manner, and inhibits the expressions of these cytokines in LPS-stimulated RAW 264.7 macrophage cells. These data indicate that (1) ASR may be a potential therapeutic modulator of NO synthesis in various pathological conditions, and (2) the immunomodulatory effects of ASR may be, in part, associated with the inducing or suppression of pro-inflammatory cytokine gene expressions.