The RAD55 gene is required for radiation resistance and meiotic viability and presumably acts in recombination and recombinational DNA repair pathways. The nucleotide (nt) sequence of RAD55 from Saccharomyces cerevisiae was determined. The amino-acid sequence predicted from the nt sequence showed similarity to the RecA protein of bacteria and the RecA-like proteins from yeast: RAD51, RAD57 and DMC1. Similarity was strongest in the region of RecA that interacts with ATP cofactor.