In this study the chromosome counts of 12 populations belonging to Achillea aleppica DC. growing in the West of Iran are reported and 9 populations were selected for karyotype analysis. Results showed that the studied populations had the basic chromosome number x=9 with ploidy levels ranging from 2x to 6x, while two populations with the chromosome number 8x were determined. The B chromosomes were observed in some of the populations. A low frequency of chromosomal bridge/lagging chromosomes was observed in the all specimens. Length of chromosomes ranged from 3.74 to 10.34 µm. The karyotype formula was 14m+4sm or 13m+5sm in the populations with chromosome number 18, and 56m+10sm+6st or 50m+18sm+4st in the populations with chromosome number 72, respectively. The further karyological studies on the basis of symmetry showed that the most of the studied populations have relatively high symmetrical karyotype (2A), and only a population showed asymmetric karyotype (2B).
