A series of novel N-tert-butyl-2-aroyl hydrazine ca rbothioamides (IIa-g) and corresponding N-tert-butyl-5-aryl- 1,3,4-oxadiazol-2-amines ( IIIa-g ) have been synthesized. The former compounds (IIa-g) were obtained by the condensation of corresponding aromatic acid hydrazi de (Ia-g) and tert-butyl isothiocyanate. The hydrazine carbothioamides when cyclised with iodine-pot.iodid e in basic medium via intramolecular cyclisation ga ve N-tert- butyl-5-aryl-1,3,4-oxadiazol-2-amines (IIIa-g). These compound (IIIa-g) were successfully de-tert-butylated into 5- aryl-1,3,4-oxadiazol-2-amines ( IVa-g ) and also tested for antibacterial and antifungal activities against selected microorganisms. The structures of the synthesized c ompounds were confirmed by elemental analyses, IR, 1H-NMR and Mass spectra.