Effects of the aqueous extract of Cimicifuga heracleifolia (CHAE) on the allergic reactions were investigated. CHAE inhibited systemic anaphylaxis induced by compound 48/ 80 in mice dose-dependently. Especially, CHAE inhibited compound 48/80-induced systemic anaphylaxis 100% with a dose of 0.5mg/g body weight. CHAE significantly inhibited serum histamine levels induced by compound 48/80. CHAE inhibited histamine release from the rat peritonea] mast cells activated by compound 48/80 or anti-DNP IgE. Our studies provide evidence that CHAE will be beneficial in the treatment of anaphylias.