The Mongolian gerbil has become a model organism of increasing importance for the understanding of aging, epilepsy, the process of domestication or sociobiological questions. We report the development and characterization of the first nine polymorphic dinucleotide repeat loci in this species. Average observed heterozygosity and allele number of laboratory animals measured 0.136 (SE = +/-0.065) and 1.78 (SE = +/-0.278) compared to 0.761 (SE = +/-0.025) and 9.2 (SE = +/-0.57) found for a reference group of wild gerbils. The extreme low genetic variation observed in laboratory animals is caused by several severe population size bottlenecks due to the initial founder event and the later establishment of subpopulations. Reduced levels of allelic polymorphism in experimental animals hamper genetic mapping or parental studies. Therefore experiments relying on kinship analyses have to be carried out on wild animals. Estimates of genetic identity and parental exclusion were calculated as Pid = 2.8 x 10(-12) and Pex > 0.999 in wild gerbils. Laboratory gerbil strains show the expected high degree of genetic similarity. However, significant allele frequency differences (P < .001) between American and European gerbils at some microsatellite loci may still allow discrimination between breeding lines.