A new series of [1,2,4]triazolo[4,3-b][1,2,4,6]thiatriazine-1,1-dioxides were synthesized, charac-terized, and evaluated for their acaricidal activity against the larvae and adults of H. scupense. The title compounds were obtained via the reaction of N-alkyl(aryl)-N′-(4H-1,2,4-triazol-3-yl)amidines and sulfuryl chloride in the presence of pyridine. The structure of the synthesized compounds was confirmed by FTIR, 1H and 13C NMR, and mass spectra and elemental analyses. Adult immersion test (AIT) was performed to determine the mortality of ticks and inhibition of oviposition and hatching after application of these compounds. Larval packet test (LPT) was performed on the larvae produced from the collected ticks. All tested compounds displayed a potent acaricidal activity. Among them, 2-benzyl-3-phenyl-2H-[1,2,4]triazolo[4,3-b][1,2,4,6]thia-triazine 1,1-dioxide showed the most potent ixodicide activity with an LC50 value of 0.19 mg/mL against 0.06 mg/mL for the standard drug amitraz. Furthermore, after 24 h of exposure, this compound caused a high mortality on H. scupense larvae, as it induced 100% mortality at the highest tested concentration (1 mg/mL). [ABSTRACT FROM AUTHOR]