Technical Abstract: Tamarix ramosissima and T. chinensis are invasive weed species in western North America. Previous studies based on single locus DNA sequence data revealed some information about the invasion process, but multilocus markers can provide additional information about levels of introgression and genotype origins. We have developed primers that amplify ten polymorphic microsatellite loci from T. ramosissima; these primer pairs also successfully amplify polymorphic microsatellites from the closely related T. chinensis, a species that forms hybrids with T. ramosissima in the western USA.