We have characterized the polymorphism of the major histocompatibility complex (MHC) in the Spanish ibex (Capra pyrenaica) by sequencing the second exon of the DRB gene in six unrelated individuals from different geographic areas. Our results demonstrate that the polymorphism of the DRB gene is very reduced in the Spanish ibex, with only two major allelic lineages which show 83% nucleotide similarity. These results are likely explained by the severe population bottlenecks that this species suffered in the XIX and XX centuries. These results will contribute to the genetic characterization of the Spanish ibex and to the establishment of selection criteria for the reintroduction of this species.