Glutathione in various foods was determined by HPLC separation, after extraction with 1% perchloric acid, which was effective for removal of protein and stabilization of glutathione in the reduced form (GSH). For determination of GSH and glutathione in the oxidized form (GSSG), the HPLC effluent was monitored by UV absorbance. For selective determination of GSH, it was converted to the N- (acridinyl) maleimide (NAM) derivative before HPLC separation, and monitored by fluorescence. Bound glutathione (B-GSH) was thoroughly reduced electrolytically with a 2-mA electrical current for 10min, enabling total glutathione (T-GSH) to be readily determined. Milk cocoa powder and canned drinks, i. e. orange drink, honey lemon soda, cocoa drink and oolong tea, were supplemented with yeast extract. They were then stored within a temperature range of 3 to 37°C for 3 months. At 3°C, the GSH content was maintained in all of the samples. At 37°C, 81% of the GSH content remained in milk cocoa powder, but only 10% remained in canned acidic drinks, i. e. orange drink and honey lemon soda. On the other hand, the content of B-GSH did not change over the tested temperature range in any of the foods. Thus it is suggested that the contents of GSH and T-GSH in food can be determined by a combination of the NAM method and the electrical reduction method.