Of those exposed to Chinese restaurant food, our studies indicate that 25% report adverse reactions (Chinese restaurant syndrome (CRS)), presumably to the mono-sodium glutamate (MSG) content. The possible significance of the symptoms is discussed in the light of the known neuroexcitatory activity of MSG. It is suggested that CRS may result from a "benign" inborn "error" of metabolism that is deserving of further study, particularly in individuals with certain other metabolic abnormalities or who are on certain types of drug therapy.