Abstract: This study investigated the effect of arctigenin (Arc) on the cell activation, cytokines expression, proliferation, and cell-cycle distribution of mouse T lymphocytes. Mouse lymphocytes were prepared from lymph node and treated with Phorbol-12-myristate-13-acetate (PMA)/Ionimycin (Ion) and/or Arc. CD69, CD25, cytokines, proliferation and cell cycle were assayed by flow cytometry. The results showed that, at concentrations of less than 1.00 μmol·L^-1, Arc expressed non-obvious cell damage to cultured lymphocytes, however, it could significantly down-regulate the expression of CD69 and CD25, as well as TNF-α, IFN-γ, IL-2, IL-4, IL-6 and IL-10 on PMA/Ion stimulated lymphocytes. At the same time, Arc could also inhibit the proliferation of PMA/Ion-activated lymphocytes and exhibited lymphocyte G₀/G₁ phase cycle arrest. These results suggest that Arc possesses significant anti-inflammatory effects that may be mediated through the regulation of cell activation, cytokines expression and cell proliferation.