Mitochondrial and Other Useful SEquences (MOUSE) is an integrated and comprehensive compilation of mtDNA from hypervariable regions I and II and of the low recombining nuclear loci Xq13.3 from about 11 200 humans and great apes, whose geographic and if applicable, linguistic classification is stored with their aligned sequences and publication details. The goal is to provide population geneticists and genetic epidemiologists with a comprehensive and user friendly repository of sequences and population information that is usually dispersed in a variety of other sources.