We investigated the effects of the aqueous extract of Solanum lyratum THUNB. (Solanaceae) (SLAE) on the anaphylactic reactions. SLAE inhibited compound 48/80-induced anaphylactic shock 100% with a dose of 1.0 mg/g body weight (BW). When SLAE was pretreated at concentration ranging from 0.0001-1.0 mg/g BW, the serum histamine levels were reduced in a dose-dependent manner. Passive cutaneous anaphylaxis also inhibited to 69.3% by oral administration of SLAE (0.05 mg/g BW). Moreover, SLAE dose-dependently inhibited the histamine release from the rat peritoneal mast cells (RPMC) by compound 48/80. The level of cAMP in RPMC, when SLAE was added, significantly increased compared with that of normal control. These results indicate that SLAE possess strong antianaphylactic activity.