AbstractFifteen new 3‐arylaminomethyl‐5‐(2‐hydroxy‐3,5‐dibromophenyl)‐1,3,4‐oxadiazole‐2‐thiones were synthesized and characterized by their sharp melting points, elemental analyses and ir spectra. These substituted oxadiazolylthiones were evaluated for their enzyme inhibitory activity. All compounds inhibitedin vitromonoamine oxidase and succinate dehydrogenase activity of rat brain homogenates. The degree of monoamine oxidase inhibition ranged from 59‐93% at a final concentration of 1 × 10−4Mwhereas the inhibition of succinate dehydrogenase was 49‐100% at a final