AbstractDue to recent population declines in tropical gar (Atractosteus tropicus), a greater understanding of its population structure is needed. A key step in gaining this understanding is the development of microsatellite loci for use in this species. For this purpose, 33 microsatellite loci from alligator gar (A. spatula) were screened in 52 individuals from a population in Zanjón del Chino, El Salvador. Twenty-five of these loci successfully amplified in this species, and 9 of those loci were polymorphic in this population. These loci should provide a useful tool for genotyping A. tropicus, both in studying existing wild populations and in monitoring genetic diversity in aquaculture.