A series of new 7H-7-alkoxy-3-alkyl/phenyl-6 aryl-s-triazolo[3,4-b][1,3,4]thiadiazines (3, 4) were synthesized by the reaction of various a,a-dibromoacetophenones 1 with 3-alkyl/phenyl-4-amino-5-mercapto-s-triazoles (2) in different alcoholic solvents in good yields. All the newly synthesized compounds (3, 4) were screened for their in vitro antibacterial and antifungal activity. Biological activities of these compounds were compared with those of the commercially available antibiotic, ciprofloxacin and antifungal agent, amphotericin-B. The title compounds showed good activity against the Gram-positive bacteria, Staphylococcus aureus and Bacillus subtilis and the yeasts, Saccharomyces cerevisiae and Candida albicans.