This paper reviews the most important factors affecting the degradation and drug-release rate of bio-erodible polymers for better control in biomedical applications. There are several factors that influence the overall rate of degradation, in addition to pH and copolymer composition. In general, polymer degradation is accelerated by greater hydrophilicity in the backbone or end groups, lesser crystallinity, lower average molecular weight, and smaller size of the finished device. At the moment, literature reflects contradictions about the role played by chemically reactive additives, crystallinity and degradation path. Factors affecting degradation and drug-release rate are discussed in their decreasing order of importance, including intrinsic properties of polymers and processing parameters.