In this review the authors discuss the polymer chemical, physical and cell biological aspects of poly (DL-lactic acid/glycine) copolymers, both in vitro and in vivo. The mechanism and rate of degradation and the degree of foreign body reaction were evaluated as a function of the molecular composition of the (co)polymer, its initial molecular weight and changes in crystallinity. Data from the literature concerning poly(lactic acid), poly(glycolic acid) and poly(amino acids) are included in this review. The choice to apply the polymers mentioned was determined by their nature: all are present in the human body as natural residues. Upon degradation, biocompatibility will thus not be impaired. The authors conclude that the degradation mechanism of poly(lactic acid), poly(glycolic acid) and poly(amino acids) are similar, i.e. bulk hydrolysis of ester bonds. The initial molecular weight and the chemical composition, determine the rate of degradation and the degree of foreign body reaction.