The FAU gene is the cellular homologue of the fox sequence in the Finkel-Biskis-Reilly murine sarcoma virus (FBR-MuSV). FAU (for FBR-MuSV associated ubiquitously expressed gene) encodes the ribosomal protein S30 fused to a ubiquitin-like protein. A cosmid clone containing the human FAU gene was used for fluorescence in situ hybridization to metaphase chromosomes. The obtained localization to 11q13 was confirmed by hybridization against a panel of somatic cell hybrids containing different parts of chromosome 11 on a hamster background. FAU was then further mapped, both on a panel of radiation-reduced somatic cell hybrids designed to carry different parts of the 11q13 region and by pulsed-field gel electrophoresis. This fine mapping assigned FAU close to the skeletal muscle glycogen phosphorylase gene (PYGM), in a region that contains several oncogenes as well as the putative tumor suppressor genes MEN1 and ST3.