The use of mouthwashes with high ethanol content has been linked to excess risks of mouth cancer, as have prolonged and frequent use of mouthwashes with lower ethanol contents. Twenty two proprietary mouthwashes available without prescription in Ireland were analysed by gas chromatography and their ethanol contents (w/v) at manufacturers' recommended dilutions for use were calculated. The ethanol contents of diluted mouthwashes ranged from < 0.01-23.40% w/v. 27% had ethanol contents > 10% w/v; 9% had ethanol contents > 20% w/v. As the use of the higher ethanol content mouthwashes may be a possible risk factor for oral cancer in frequent or constant users, we believe that the attention of the statutory regulatory authorities should be drawn to this situation.