Lignans fromVirola sebifera Aubl.,Virola sp., andOtoba parvifolia (Mkfg.) A. Gentry (Myristicaceae) inhibited the in vitro growth of the fungus cultivated by leaf-cutting ants of the speciesAtta sexdens rubropilosa Forel (Hymenoptera: Formicidae). A comparison of activity among the lignans was obtained.