In this study we show that the previously described uvs112 (uvs12) mutation blocks one of the steps of the excision repair pathway. The properties of this mutation permit the assignment of the UVS112 gene to the RAD3 epistasis group. It was established that the uvs112 mutation caused a 2.5-fold reduction in the number of recombinants produced by conversion and also significantly increased the frequency of mitotic crossing-over in interplasmid recombination. Tetrad analysis placed the UVS112 gene on the left arm of chromosome IX, approximately 20 cM from HIS5. The analysis of mitotic recombination revealed that UVS112 lies between HIS6 and HIS5, and is an allele of the RAD25 gene.