Karyotype and meiotic studies were performed in 16 populations of seven Arenaria species growing in Iran. All the species studied showed 2n = 2x = 22 chromosome number supporting the earlier report on A. persica, A. insignis and A. gypsophiloides while the chromosome numbers of A. polycnemifolia, A. zargariana, A. szowitsii and A. minutissima are new to science. The chromosomes were mainly metacentric and submetacentric. The species studied differed significantly in total size of the chromosomes, size of the short arms and the long arms, indicating the role of quantitative genomic changes in the Arenaria species diversification. They also differed in their karyotype formulae indicating the occurrence of structural changes in their chromosomes. Meiotic analysis showed quadrivalent formation in Moorchegan population of A. persica and Kandovan population of A. insignis possibly due to the occurrence of heterozygote translocation between two pairs of chromosomes which in turn may increase the amount of genetic variability in the next generation. Cytomixis led to the formation of unreduced pollen grains in Mishoodagh population of A. gypsophiloides var. glabra, while B-chromosomes were observed in A. insignis and A. polycnemifolia species.