The soluble selenium (Se) compounds selenic acid, selenious acid, selenium dioxide, selenium tetrachloride, selenomethionine, selenourea, sodium selenate and sodium selenite broke the dormancy of scarified seeds of Townsville stylo (Stylosanthes humilis HBK). Given the chemical diversity of all these molecules, it could be deduced that Se may act as a dormancy- breaking agent of Townsville stylo seeds. Sestimulated seeds produced great amounts of both ethylene and 1-aminocyclopropane-1-carboxylic acid, which correlated with the process of germination. As specific inhibitors of ethylene biosynthesis and action largely depressed this Se-stimulated germination, it was concluded that Se broke dormancy by triggering ethylene production by the seeds.