Melamine/Formaldehyde Resin is intended for use as a film former in cosmetic formulations, but there are no current uses reported. Respiratory distress, bleeding in the lungs, significant weight loss, and macrophage influx into the alveoli were observed during inhalation studies in rats. A 2-year chronic feeding study in rats at concentrations ≥ 10% produced little toxicity. Similar results were found in dogs at concentrations of 2.5, 3, and 5%. Reproductive toxicity was evaluated in rats through two generations with no evidence of reproductive effects. Case reports in the clinical literature have reported sensitization to Melamine/Formaldehyde Resin, not all of which were attributed to the presence of formaldehyde. Available data on melamine were reviewed. No irritation or sensitization was produced by 1% (aqueous) melamine in guinea pigs. In an oral carcinogenesis assay in male rats, melamine caused transitional-cell carcinomas of the urinary bladder, but produced no tumors in female rats. Adverse effects of formaldehyde were summarized from an earlier review of that ingredient by the Cosmetic Ingredient Review. The adverse effects included respiratory damage, skin irritation and sensitization, and carcinogenesis. The available data were insufficient to support the safety of Melamine/Formaldehyde Resin. Additional data were considered necessary in order to evaluate the safety of this ingredient, including chemical and physical data (such as p H), amount of free formaldehyde as a function of p H, and the aqueous or alcohol vehicle used; impurities (or purity); physical form of the ingredient as it would be used; UV absorption data (if the ingredient absorbs in the UVB or UVA regions of the electromagnetic spectrum, photosensitization studies would be needed); 28-day dermal toxicity tests; and human irritation and sensitization. It cannot be concluded that this ingredient is safe for use in cosmetic products until the listed safety data have been obtained and evaluated.