Glycerol chlorohydrines, such as 3-chloro-1,2-propanediol and 1,3-dichloro-2-propanol, are present in commercial protein hydrolysates used for human nutrition. These compounds are genotoxic and 1,3-dichloro-2-propanol induced tumors in rats. Now it is reported that both compounds are active at inducing malignant transformation of mouse fibroblasts. Therefore, the carcinogenic risk to humans by exposure to these compounds contained in food is of concern. The investigation of the in vivo carcinogenic potential of 3-chloro-1,2-propanediol is urgently required to further evaluate the carcinogenic risk to exposed consumers.