Work was continued on the pharmacological study of the 1,3,4-oxadiazole nucleus using aroylhydrazines already used for the synthesis of anti-MAO compounds. S-alkylaminoalkyl derivatives of some 2-mercapto-5-aryl-1,3,4-oxadiazoles were prepared bearing in the 5-position a 3,4,5-trimethoxyphenyl, a 3,5-dimethoxy-4-ethoxyphenyl or a 3,4-dihydroxymethylenephenyl radical. When subjected to pharmacological investigation the compounds showed clear hypotensive activity partially antagonized by atropine and antispastic activity on smooth muscle.