Clematis mandshurica Rupr (Ranunculaceae) roots are used in traditional Korean medicine to treat inflammation-related diseases. Therefore, we undertook to investigate their inhibitory effect on inflammation under non-cytotoxic conditions. The ethanolic extract of Clematis mandshurica at 100 microg/ml was found to significantly block the production of the pro-inflammatory mediators, nitric oxide (NO) and prostaglandin E(2) (PGE(2)), in lipopolysaccharide (LPS)/interferon(IFN)-gamma-stimulated mouse peritoneal macrophages, by up to 77% and 59%, respectively. In addition, it significantly inhibited cell proliferation and cytokine production (interleukin (IL)-2 and IFN-gamma) in splenocytes stimulated with Con A (concanavalin A; 5 microg/ml). Furthermore, when splenocytes from extract fed mice (200 mg/kg for 2 weeks) were activated with Con A, cell proliferation and the production of IL-2 and IFN-gamma were significantly inhibited. In addition, the extract reduced in vivo inflammation in oxazolone-induced delayed type hypersensitivity (DTH) model mice. Taken together, these data suggest that Clematis mandshurica is able to ameliorate inflammatory disease by exerting an anti-inflammatory effect in cases of proinflammatory and cell-mediated inflammation.