Objective: Previously, the methanol extracts of the semen of Xanthium strumsrium could involved anti-inflammatory effects in lipopolysaccharide (LPS)-stimulated Raw 264,7 cells, We evaluated the anti-allergic effects of X. strumarium on rat basophilic leukemia (RBL-2H3) cells, Methodes : To investigate the effect of X. strumarium on the phorbol 12-myristate 13-acetate (PMA) and calcium ionophore A23187-induced RBL-2H3 cells. The effects of X. strumarium on the degranulation and the pro-inflammatory cytokines secretion and expression from RBL-2H3 cells were evaluated with $eta$-hexosaminidase assay, ELISA, and RT-PCR analysis, In addition, we examined the effects of X. strumarium on nuclear factor (NF)-${kappa}B$ activation and $I{kappa}B-alpha$ degradation using Western blot analysis. Results : X. strumarium inhibited degranulation and secretions and expressions of pro-inflammatory cytokines, such as tumor necrosis factor-alpha ($TNF-alpha$), interleukin (IL)-4 and cyclooxygenase (COX)-2, on stimulated RBL-2H3 cells, however, X. strumarium not affect cell viability. In stimulated RBL-2H3 cells, the protein expression level of nuclear factor-kappa B (NF-${kappa}B$) was decreased in the nucleus by X. strumarium. In addition, X. strumarium suppressed the degradation of inhibitory protein $I{kappa}B-{alpha}$ protein in RBL-2H3 cells. Conclusion : These results suggest that X. strumarium inhibits the degranulation and secretion of pro-inflammatory cytokines through blockade of NF-${kappa}B$ activation and I $I{kappa}B-{alpha}$ degradation.