The NHA1 gene (2958 nt) encoding a putative Na(+)/H(+) antiporter (986 aa) in Saccharomyces cerevisiae was cloned by selection based on increased NaCl tolerance. The putative protein is highly similar to sodium/proton antiporters from Schizosaccharomyces pombe (gene sod2), and Zygosaccharomyces rouxii (gene Z-SOD2). Overexpression of the NHA1 gene results in higher and partially pH-dependent tolerance to sodium and lithium; its disruption leads to an increased sensitivity towards these ions.