Dye removal by acid-treated chitin was investigated and compared with results from chitosan. Dyes used were Acid Blue 25, Direct Red 81 and Mordant Yellow 10 which were all anionic dyes. When the pH of initial dye solution was 6, the dye removal of the acid treated chitin was superior to those of untreated chitin and chitosan. Dye removal was varied with the moisture content of the acid treated chitin and increased as the moisture content was increased. Also, dye removal was varied very sensitively with the pH of dye solution and increased as pH was decreased. When the pH of initial dye solution was 6, the dye removals of acid-treated chitins were significantly higher than those of untreated chitin and chitosan. But, at pH 3, the dye removal of chitosan was the highest among them.