The chemical structure of polymers obtained through enzyme-catalyzed reactions can be controlled by the addition of chemical structure-controlling templates. Examples are reviewed and discussed. Although this concept is applied successfully, it seems to be limited to polymerization reactions which are initiated by certain oxidoreductases (for example peroxidases or laccases). This conclusion is based on the consideration of (i) selected examples of enzymatic in vitropolymerizations and (ii) some of the key features of the biosynthesis of biopolymers.