Chromosome counting was performed in nine populations of Achillea tenuifolia Lam and eight populations of A. bieberestinii Afan (Asteraceae) collected from Hamedan and Kermanshah provinces in the west of Iran. Chromosome numbers in both species varied from 2n=2x=18 to 2n=4x=36. Some populations of both species showed (2n=4x=36) chromosome number that is the first report as polyploidy levels. Aneuploidy is also the first report for both species. Diploid and tetraploid individuals were observed in some populations at the same locality. B-chromosomes were observed in some populations of both species. The results indicated that polyploidy is a common future in this species similar to other Asteraceae plants.
