The Galápagos Giant Tortoise (Geochelone nigra) is a seriously endangered species. Eleven sub-species survive on six islands, the largest island displaying 5 sub-species isolated from each others on different volcano slopes. Most of these populations are small, and even the largest populations are in danger of extinction due to human activity. We have isolated >300 G. nigra microsatellite loci of which a subset will be used to assess the genetic diversity of the various populations of the Galápagos archipelago. In particular, these data will allow us to assist an ongoing captive breeding program for the population from the Espanola Island. We will determine parentage of individuals born in captivity in order to objectively determine the crosses to be favored for maximizing the genetic diversity of this population.