Xiphophorus is a genus consisting of 26 species of small, freshwater, live-bearing fish species. Distinct biological traits make Xiphophorus fish useful in a broad array of research topics that include behavioral, evolutionary, physiological, developmental, toxicological, genomics, immunological, and parasitological studies. More specifically to our program, they have been used to study metabolism, sex determination, maturation, chronobiology, cancer, bioinformatics, and optical genetic regulation. The Xiphophorus Genetic Stock Center (XGSC; www.xiphophorus.txstate.edu) is a national animal resource center in the US that currently hosts 24 of 26 known Xiphophorus species and over 60 different strains within those species maintained for specific genetic traits, as well as a variety of inter-species hybrids. The XGSC has ~10,000 live fish maintained in ~1,400 aquaria. In addition to housing the Xiphophorus fish species, the center performs multiple additional duties: analysis of biopsy material, distribution of conserved biological materials, and consultation on husbandry and genetic questions. Further, the center provides resources that are relevant to Xiphophorus animal husbandry, histology, genomes, transcriptomics, protocols, and software for research purposes.