A renewed interest in aliphatic polyesters has resulted in developing materials important in the biomedical and ecological fields. Mainly materials such as PLA and PCL homopolymers have so far been used in most applications. There are many other monomers which can be used. Different molecular structures give a wider range of physical properties as well as the possibility of regulating the degradation rate. By using different types of initiators and catalysts, ring-opening polymerization of lactones and lactides provides macromolecules with advanced molecular architectures. In the future, new degradable polymers should be able to participate in the metabolism of nature. Some examples of novel polymers with inherent environmentally favorable properties such as renewability and degradability and a series of interesting monomers found in the metabolisms and cycles of nature are given. A.-C. Albertsson, I.K. Varma: Aliphatic Polyesters: Synthesis, Properties and Applications.- K.M. Stridsberg, M. Ryner, A.-C. Albertsson: Controlled Ring-Opening Polymerization: Polymers with Designed Macromolecular Architecture.- U. Edlund, A.-C. Albertsson: Degradable Polymer Microspheres for Controlled Drug Delivery.- M. Hakkarainen: Aliphatic Polyesters: Abiotic and Biotic Degradation and Degradation Products.- M. Söderqvist Lindblad, Y. Liu, A.-C. Albertsson, E. Ranucci, S. Karlsson: Polymers from Renewable Resources.-
