The reaction of substituted benzoic acid hydrazide with carbondisulfide and potassium hydroxide followed by treatment with hydrazinehydrate afforded 4-amino-5-aryl-4H-1, 2, 4-triazole-3-thiol (4). Condensation of (4) with various aromatic carboxylic acids in the presence of phosphorus oxy chloridegives 3,6disubstituted- [1,2,4]triazolo[3,4b][1,3,4]thiadiazoles(5) and with various aroylthiocyanate in the presence of ethanol gives N,3 disubstituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazol-6-amine (6). The structure of these newly synthesized compounds was characterized by elementalanalysis, IR, 1H NMR studies. All the synthesized compoundswere screened for their antibacterial activity against H.pylori, P.aeroginosa, E.coli, S.aureus and Methcyclin resistant strain(MRSA) and antifungal activity against A.niger, A.foeniculum and P.chrysogenum. Some of compounds exhibited promising antibacterial and antfungal activities.Most active antifungalcompound was4a (4-amino-5- phenyl-4H-1, 2, 4-triazole-3-thiol) with MIC (Minimum Inhibitory Concentration) 57.14 μg/ml and Zone of inhibition 14 mmagainst A.foeniculum. Most potent antibacterial compound was5b (3-(4-nitrophenyl)-6-phenyl-[1, 2, 4]-triazolo [3, 4-b] [1, 3, 4] thiadiazole) with MIC 10 μg/ml, Zone of inhibition 8mmagainst H.pylori.