Karyotype analysis is considered an important prerequisite for fruit tree genetic and breeding studies. In this study observations were carried out on Cornus mas L. genotypes from Arasbaran forests and Kaleibar district in Iran. The root tips were pretreated with 8-Hydroxiquinolin, then fixed in Lewitsky solution and stained in Aceto-Iron-Haematoxylin (composed of 4% haematoxylin and 1% iron alum in 45% acetic acid). Ten metaphasic plates were used to analyze karyotype parameters. The results confirmed the existence of 2n = 2x = 18 chromosomes. The karyotypic formula was 2n = 2x = 18 = 8m + 2sm(sat) + 8sm, with the centromeres having median and sub median position. Chromosome size ranged between 11.33 +/- 0.54 to 6.60 +/- 0.19 mu m. The length of haploid complement was 71.54 mu m. Centromeric index were varied from 24.27 to 46.53, while the arm ratio values comprised in 1.15-2.72 intervals.