Cytogenetic studies of Philodryas nattereri and Philodryas olfersii revealed a diploid chromosome number 2n = 36 for both species (3 metacentrics, 4 submetacentrics, and 10 acrocentrics, with a fundamental number of 51 and 52, respectively). The results obtained are novel and similar to those previously described for species belonging to the Dipsadidae family. The conventional karyotype is also novel and divergent from other species of the Dipsadidae family, where a higher proportion of macrochromosomes predominate, revealing two distinct groups in this family. The data are reported and discussed considering the cytotaxonomy of the family. These results strongly support the current view that chromosomal alterations, such as centric fusion and Robertsonian's translocations, seems to support the distinct importance of chromosomal rearrangements in speciation within this group.