This safety assessment addresses cosmetic ingredients that are N-acyl derivatives of sarcosine and are generally referred to as acyl sarcosines, and those that are salts, known generally as acyl sarcosinates. Previous assessments have addressed the safety of each of the fatty acids that appear in these acyl sarcosines and sarcosinates (Coconut Acid, Oleic Acid, Lauric Acid, and Myristic Acid). In each case the fatty acid was either safe for use or safe as used in cosmetic formulations. Acyl sarcosines are considered modified fatty acids with greater solubility and increased acidity of the carboxylic acid group compared to the parent fatty acid. They are used in a large number of cosmetic formulations as hair-conditioning agents and surfactant-cleansing agents. In soaps, concentrations are reported to be as high as 12.9%. These ingredients have low oral toxicity in rats. Although cytotoxic to Chinese hamster cells in culture, acyl sarcosines and sarcosinates are not mutagenic in those cells, nor in bacterial cells in culture. Carcinogenicity data were not available. These ingredients are nonirritating and nonsensitizing to animal and human skin, although they can enhance the penetration of other ingredients through the skin. For that reason, caution should be exhibited in formulating cosmetic products that contain these ingredients in combination with other ingredients whose safety is based on their lack of absorption or where dermal absorption is a concern (e.g., HC Yellow No. 4, Disperse Yellow 3). Because sarcosine can be nitrosated to form N-nitrososarcosine, a known animal carcinogen, these ingredients should not be used in cosmetic products in which N-nitroso compounds may be formed. With the above caveat, and based on the available data, it was concluded that these acyl sarcosines and sarcosinates are safe as used in rinse-off products. They may be safely used in leave-on products at concentrations up to 5%, the highest concentration tested in clinical irritation and sensitization studies. Oleoyl Sarcosine is used as a corrosion inhibitor in some aerosol products, at extremely low concentrations. In this circumstance, the ingredient is not being used as a cosmetic ingredient and this report is not intended to limit that use. Because of the absence of data on inhalation toxicity, however, it was concluded that the available data were not sufficient to support the safety of acyl sarcosines and sarcosinates as cosmetic ingredients in products where they are likely to be inhaled.