We have isolated a mutant of the yeast Schizosaccharomyces pombe which exhibits sensitivity to UV light when grown at either 30 degrees or 37 degrees C, as compared to the parental wild-type strain. This increased sensitivity is more pronounced when cells are grown at 37 degrees C. The mutant is also sensitive to 18 MeV electrons at the high temperature. Tetrad analysis of spores generated by crossing the mutant and a Rad+ strain revealed that sensitivity to both types of radiation cosegregate 2:2, relative to wild-type resistance, indicating that a single altered chromosomal locus is responsible for the radiation sensitivities observed. In addition, analysis of spores resulting from crosses between the mutant and all other known S. pombe rad mutants indicates that the temperature-dependent sensitivity described in this report is mediated by a mutation in a previously unidentified rad locus.