Resveratrol (1) and nine related hydroxystilbene compounds (2 approximately 9) isolated from plants were evaluated for the anti-allergic activities in vitro. Resveratrol (1) and rhapontigenin (5) demonstrated significant inhibitions upon the release of beta-hexosaminidase from the cultured RBL-2H3 cells in a dose-dependent manner and the IC50 values were calculated as 14 and 15 microM, respectively.