A series of thiazolo[3,2-b][1,2,4]triazole incorporating diphenylsulfone moieties were synthesized starting from 5-[4-(4-X-phenylsulfonyl)phenyl]-4H-1,2,4-triazole-3-thioles 3a-c, X=H, Cl, Br. Thus, alkylation of 1,2,4-triazoles 3 with phenacyl bromide or 4-bromophenacyl bromide afforded S-substituted 1,2,4-triazoles 4, 5. These new intermediates 4 and 5, in the presence of H(2)SO(4) (c), were cyclized to 2-[4-(4-X-phenylsulfonyl)phenyl]-6-(4-Y-phenyl)[1,3]thiazolo[3,2-b]-[1,2,4]-triazoles 6, 7 (I) and not to isomeric thiazolo[2,3-c][1,2,4]-triazoles 6, 7 (II). The newly synthesized compounds were characterized by IR, (1)H, (13)C NMR and elemental analysis. MS spectra confirmed the formation of thiazolo[3,2-b][1,2,4]triazole 6, 7 (forms I) in detriment of [2,3-c] isomeric compounds (forms II). The potential antibacterial effects of the synthesized compounds were investigated using standard bacterial strains: Acinetobacter baumannii ATCC 19606, Citrobacter freundii ATCC 8090, Escherichia coli ATCC 11775, Pseudomonas aeruginosa ATCC 9027, Enterococcus faecalis ATCC 19433, Staphylococcus aureus ATCC 12600, Staphylococcus epidermidis ATCC 14990, Bacillus cereus ATCC 14579.