Macrocyclic polyethers (crown ethers) are a family of compounds which possess the ability to transport ionic species across natural and artificial membranes. Because of this characteristic, they have wide applications in industry and are being investigated for their potential as pharmacologic agents. However, these compounds are highly cytotoxic in both prokaryotes and eukaryotes. Because of the cytotoxicity of crown ethers, an investigation of the potential genotoxicity of these compounds in Salmonella typhimurium was initiated. Several unsubstituted and substituted crown ethers did not induce a genotoxic response in S. typhimurium strains TA100, TA1530, TA98 and TA1537 either with or without rat liver S9 mixture. The data support the conclusion that the toxicity of these compounds is probably not due to an interaction with nucleic acid to induce premutagenic lesions and they do not appear to be genotoxic in prokaryotes.