A prodecure for the quantitative determination of lysinoalanine (LAL) by gas chro-matography-selected ion monitoring was developed. α,e-Diaminopimelic acid was chosen as the internal standard, and the content of LAL in commercial foods was analyzed. Of the samples analyzed, the content was highest in pidan. Wheat flour-based products (Chinese noodles, pretzels and crackers) and milk products (condensed milk and lactic acid beverages) also contained a significant amount of LAL. Ordinary milk, soybean (soy milk and soy protein isolate) and meat products (ham and Hamburg steak) contained a low amount of LAL. It was confirmed that the possibility of low-level LAL formation existed in foods cooked at home without any alkaline treatment.