In this article, we describe a novel, widespread domain (CASH) that is shared by many carbohydrate-binding proteins and sugar hydrolases. This domain occurs in more than 1000 proteins distributed among all three kingdoms of life. The CASH domain is characterized by internal repetitions of glycines and hydrophobic residues that correspond to the repetitive units of a predicted or observed right-handed beta-helix structure of the pectate lyase superfamily.