Ticks are hematophagous arthropods transmitting several harmful human and animal pathogens like viruses, Rickettsia, bacteria, and protozoa. The identification and speciation of ticks were normally performed in Iran using identification key of Arthur (1960) and Kaiser and Hoogstraal (J Parasitol 49:130-139, 1963) or on the basis of morphological characteristic keys recommended by Walker et al. (2003). Although these identification keys are well prepared, but there are in some cases due to the strong overlapping characteristics between species like Dermacentor marginatus and Dermacentor niveus accompanied with serious problems. D. marginatus and D. niveus have been intermittently used synonymously and there is no a generally agreement with the specification of these species. To find out more about these two species, we have analyzed the complete nucleotide sequence of ITS-2 region. Interestingly, we found indeed a sequence homology of 99% between nucleotide sequence of ITS-2 region of D. marginatus and D. niveus. Since the nucleotide sequence of ITS-2 region of D. marginatus in Iran has 98% sequence homology to the other in GenBank registered ITS-2 sequence of D. marginatus, and the morphological characteristics between both examined species showed minimal differences, therefore we believe that the D. marginatus and D. niveus could belong to the same species and 1% differences in nucleotide sequence of ITS-2 region between these two species can be understand as an intra-species polymorphism.