5-[4-(4X-phenylsulfonyl)phenyl]-1,3,4-oxadiazole-2-thiols, X=H, Cl, Br, reacted with ethyl chloroacetate to give S-alkylated compounds. Aminomethylation of the thione form of oxadiazoles yielded N(3)-derivatives. All the products have been characterized by elemental analysis, IR, 1H-NMR and 13C-NMR. The plant-growth regulating effects of the title compounds were examined. From the biological activity results, we found that most compounds showed weak stimulatory activities at low concentrations.