This study was conducted to evaluate the inhibitory effects of Yongseollan(YSL) on the production of nitric oxide (NO) and the expression of inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated RAW264.7 cells. YSL is tropical plant originating from Mexico. The biological activity of this plant is not yet evaluated systematically. The aim of the present work is to investigate a potential anti-inflammatory activity of YSL. The RAW264.7 cells were cultured in D MEM/F12 medium for 24 hrs. After serum starvation, cells were treated with YSL for 1 hr, followed by stimulating NO production with a LPS. We found that YSL has an inhibitory effect on the production of NO, iNOS expression and $phospho-I{kappa}B$ expression. YSL also inhibited tumor necrosis factor $(TNF)-{alpha}$, interleukin (IL)-6, and $IL-1{eta}$. Moreover, YSL inhibited cyclooxygenase (COX)-2 expression and prostanglandin E2 (PGE2). These findings showed that YSL could have some anti-inflammatory effects which might play a role in therapy in Gram-negative bacterial infections.