We report a case of Cronkhite-Canada syndrome in a 66 year-old man, particular by an association with arsenism. Both arsenism and the Cronkhite-Canada syndrome are a cause of ectodermal and mucosal lesions. The persistence of physical, biological and endoscopic manifestations associated with disappearance of arsenic intoxication signs allowed us to make the diagnosis. The search of arsenic in blood, nail and hair must complete the investigations in case of acquired pseudopolyposis and ectodermal changes.