We investigated the effect of aqueous extract of Gleditsia sinensis thorns (Leguminosae) (GSAE) on the mast cell-dependent anaphylaxis. GSAE (0.005 to 1 ${g}/kg$) dose-dependently inhibited systemic anaphylaxis induced by compound 48/80 in rats. GSAE (0.1 and 1 ${g}/kg$) also significantly inhibited local anaphylaxis activated by anti-DNP IgE. When GSAE was pretreated at the same concentrations with systemic anaphylaxis, the plasma histamine levels were reduced in a dose-dependent manner. GSAE (0.001 to 1 ${m}g/ml$) dose-dependently inhibited the histamine release from rat peritoneal mast cells (RPMC) activated by compound 48/80 or anti-DNP IgE. The level of cyclic AMP in RPMC, When GSAE (1 ${m}g/ml$) was added, transiently and significantly increased about fourfold compared with that of basal cells. Moreover, GSAE (0.01 and 0.1 ${m}g/ml$) had a significant inhibitory effect on anti-DNP IgE-induced tumor necrosis factor-$alpha$ production from RPMC. These results suggest a possible use of GSAE in managing mast cell-dependent anaphylaxis.