The reaction of 3,5-bistrifluoromethyl phenyl acid hydrazide with carbon disulfide and potassium hydroxide followed by treatment with hydrazine hydrate afforded 5-(3, 5-bis(trifluoromethyl) phenyl) -4-amino-4H-1,2,4- triazole-3-thiol. Condensation of (6) with various aromatic carboxylic acids or with phenacyl bromides afforded two series of fused heterocycles namely 6-(substituted aryl)-3-(3,5-bis(trifluoromethyl)phenyl)-[1,2,4]triazolo[3,4- b][1,3,4]thiadizoles (7) and 6-(substituted aryl)-3-(3,5-bis(trifluoromethyl)phenyl)-7H-[1,2,4]triazolo[3,4- b][1,3,4]thiadiazines (8), respectively. All the synthesized compounds were screened for their antibacterial and antifungal activities. Some of the compounds exhibited promising antimicrobial activities.