The IgE-suppressive activity of (-)-matairesinol is demonstrated, and the structure-activity relationship of (-)-matairesinol clarified. 3',4-Dihydroxy-3,4'-dimethoxylignano-9,9'-lactone showed higher IgE-suppressive activity than (-)-matairesinol without any cytotoxic activity. Some derivatives bearing a longer and more bulky alkoxy group at the 3 or 4 position showed IgE-accelerative activity.