Abstract: Polymer salts whose anionic component is a polyester which comprises the product of reaction of the individual components a), b) and c) and if desired d) and if desired e), wherea) is a dicarboxylic acid or a reactive derivative of a dicarboxylic acid, being free from sulfo groups,b) is a difunctional aromatic, aliphatic or cycloaliphatic sulfo compound whose functional groups are hydroxyl or carboxyl, or hydroxyl and carboxyl,c) is an aliphatic, cycloaliphatic or aromatic diol, a polyetherdiol or a polycarbonatediol,d) is a polyfunctional compound (functionality>2) whose functional groups are hydroxyl or carboxyl, or hydroxyl and carboxyl, ande) is a monocarboxylic acidand whose cationic component comprises hydrogen atoms, metal cations, substituted ammonium cations, immonium cations, guanidinium cations, phosphonium, arsonium or stibonium cations or a mixture of the abovementioned cations, are suitable as charge control agents and charge improvers in electrophotographic toners and developers, in triboele