Three DNA repair genes, ERCC1, ERCC2, and XRCC1, have been regionally mapped on human chromosome 19. ERCC2 and XRCC1 have been assigned to bands q13.2----q13.3 by in situ hybridization using fluorescently-labeled cosmid probes. ERCC1 and ERCC2 have been found to be separated by less than 250 kb by large fragment restriction enzyme site mapping.