The effect of the aqueous extract of Alpinia oxyphylla Miq. (Zingiberaceae) fruits (AOFE) on anaphylactic reaction was investigated. AOFE completely inhibited compound 48/80-induced systemic anaphylactic shock at dose of 1.0 g/kg. When AOFE was pretreated at concentrations ranging from 0.01 to 1.0 g/kg, the plasma histamine levels induced by compound 48/80 were reduced in a dose-dependent manner. AOFE also inhibited the histamine release from rat peritoneal mast cells (RPMC) by compound 48/80. The level of cAMP in RPMC, when AOFE was added, transiently and significantly increased about 4-fold compared with that of basal cells. These results indicate that AOFE may be beneficial in the treatment of non-specific anaphylactic reactions.