Many studies have been reported on the marked effectiveness of chlortetracycline for the preservation of round fish (3,7,8,(14)(15)(16)(17)(18)(19)(20).For the commercial use of chlortetracycline, however, government approval of the respective country is required. As an approach to realize this goal, it was necessary to make a survey of chlortetracycline residue in the flesh of fish which was subjected to various practical treatments with chlortetracycline.