We have cloned the RAD10 gene of Saccharomyces cerevisiae and physically mapped it to a 1.0-kb DNA fragment. Strains containing disruptions of the RAD10 gene were found to show enhanced UV sensitivity compared with the previously characterized rad10-1 or rad10-2 mutants. The UV sensitivity of the disruption mutant is comparable to the highly UV sensitive rad1-19, rad2-delta, and rad3-2 mutants.