Changes in amines (tyramine, putrescine, cadaverine, agmatine, and tryptamine) were examined in the muscle of common squid during storage at O"C, 3S"C, and 15°C. Agmatine appeared to be most useful as a potential index for freshness of common squid. Agmatine was detected in small amounts even in the fresh muscle and the concentration increased with storage time, exceeding 30 mg/lOOg at the stage of initial decomposition and reached the level of 40 mg/lOOg at the stage of advanced decomposition. Putrescine was detected in small amounts (less than 1 mg/lOOg) at the stage of initial decomposition and increased rapidly at the stage of advanced decomposition. This amine might be involved in the putrid smell. The pH values became higher at the stage of initial decomposition.