Chloroform and methanol extracts of the fruits of Melaleuca lencadendron strongly inhibited histamine releaes from rat mast cells induced by compounds 48/80 or concanavalin A. Ursolic acid, a triterpene, was the most active compound contained in the chloroform extract and two stilbenes, piceatannol and oxyresveratrol, were isolated as active compounds from the methanol extract. Several other stillbenes and related compounds were examined to obtain information on the structure activity relationships of stilbenes.