Pistacia genus belongs to the Anacardiaceae family, and comprises only dioecious species. These plants are distributed between 29 degrees and 42 degrees north. All species of this genus are diploid with chromosome numbers of 2n equal to 24, 28 and 30. According to literature, the basic chromosome number in this genus is x equal to 12, 14 and 15. Pistacia khinjuk with a chromosome complement of 2n equal to 24 has a symmetric karyotype with a median and submedian centromere position. Because ancestral species have a symmetric karyotype, it seems that x equal to 12 is the initial basic chromosome number in this genus and the x equal to 14 and x equal to 15 derived from x equal to 12. No polyploid races have been reported in Pistacia so far, so it seems that diploidy phenomena played an important role in evolution and speciation.