The naturally occurring bialdehyde Glyoxal is used as a preservative in nail polishes and enamels. It is provided to formulators as a 40% aqueous solution because the nonhydrated form is highly reactive with water and other solvents. Reduced weight gain was seen in acute and subchronic animal studies, glyoxalase levels increased in the first 30 days, and hemorrhages of the mesenteric lymph nodes were found across a wide range of doses. Glyoxal readily forms DNA adducts at purine sites. Glyoxal is mutagenic in a wide range of systems, and oral studies indicate that it can act as a tumor promoter, but not an initiator. Clinical data indicate no evidence of sensitization. These data are insufficient to evaluate the safety of Glyoxal. Additional safety data are needed, including a dermal carcinogenesis study using the skin painting methods of the National Toxicology Program; impurities, especially with respect to selenium, chlorinated organic compounds, and the Glyoxal monomer; and current data on the types of products in which Glyoxal is used and at what concentrations. It is recognized that there are no reproductive or developmental toxicity data available to analyze-depending on the results of the studies described, additional data may be requested. It cannot be concluded that this ingredient is safe for use in cosmetic products until the listed safety data have been obtained and evaluated.