This study was carried out to determine the effects of the 70% ethanolic extract from the anomalous fruitsof Gleditsia sinensis LAM. (AFGS) on experimental allergic reactions and inflammation. AFGS (200, 500, 1000mg/kg, p.o.) dose-dependently inhibited the systemic anaphylactic shock induced by compound 48/80 in mice andcutaneous reactions induced by histamine or serotonin in rats. At doses of 500 and 1000 mg/kg, AFGS showed aclear inhibition on homologous passive cutaneous anaphylaxis in rats. In vitro, AFGS significantly reduced histaminerelease from rat peritoneal mast cells triggered by compound 48/80 at concentrations of 20 and 50mg/ml.Moreover, AFGS (500, 1000mg/kg, p.o.) showed a significant inhibition on the hind paw edema in rats and earswelling in mice caused by carrageenin and croton oil, respectively. It also clearly inhibited the vascular permeabilityinduced by acetic acid in mice at a dose of 1000mg/kg. These findings demonstrate that the ethanolic extractfrom the anomalous fruits of Gleditsia sinensis possesses antiallergic and anti-inflammatory activities,which may be mediated by reducing the release of mediators such as histamine from mast cells and weakeningthe inflammatory action of these mediators.