Electrosurface properties of polymers are the key to various biointerfacial effects. Examples comprise the helix-coil transition in poly(L-glutamic acid) brushes, the activation of the kinin system by negatively charged surfaces and the heparin-like activity of negatively charged macromolecules. Physico-chemical studies are dedicated to the detailed characterization of the interfacial charge formation at polymers in aqueous electrolyte solutions. Focus is put on the charge formation by unsymmetrical ion adsorption, interrelations between charging and structure of biopolymers at interfaces and on the influence of charge on structural and dynamic properties of supported lipid bilayer membranes. The research on electrosurface phenomena also includes the development of new analytical techniques.