Abstract: Methods are provided for the synthesis of polymer conjugates of cytokines, chemokines, growth factors, polypeptide hormones and receptor-binding antagonists thereof, which conjugates retain unusually high receptor-binding activity. Preparation of polymer conjugates according to the methods of the present invention diminishes or avoids steric inhibition of receptor-ligand interactions that commonly results from the attachment of polymers to receptor-binding regions of cytokines, chemokines, growth factors and polypeptide hormones, as well as to agonistic and antagonistic analogs thereof. The invention also provides conjugates and compositions produced by such methods. The conjugates of the present invention retain a higher level of receptor-binding activity than those produced by traditional polymer coupling methods that are not targeted to avoid receptor-binding domains of cytokines, chemokines, growth factors and polypeptide hormones.