Structure and properties of bioabsorbable polyglycolide (PGA) and poly(glycolide-co-lactide) (PGA-co-PLA)fibers were investigated during several industrial processing stages and in vitro degradation by means of wide-angle X-raydiffraction (WAXD), dynamic mechanical analysis (DMA) and mechanical property tests. In the orientation stage, the PGAfibers were found to have higher degrees of crystallinity than corresponding PGA-co-PLA samples produced under similarconditions. In the hot-stretching and post-annealing stages, after fibers were braided, PGA samples were found to gain morecrystallinity and higher T_g than PGA-co-PLA samples. The higher crystallinity in PGA fibers resulted in a slower rate ofdegradation. DMA results showed that a great deal of internal stress that was built during orientation and hot-stretchingstages was released in the post-annealing stage for a1l PGA and PGA-co-PLA samples. During earlier stages of in vitrodegradation, both PGA and PGA-co-PLA samples exhibited the typical cleavage-induced crystallization mechanism. Theheat shrinkage in the glass transition area was found to disappear after 6-8 days of degradation for all PGA and PGA-co-PLAsamples, indicating the amorphous portions of the polymers lost orientation after a short period in the buffer solution, mostlikely due to relaxation of the cleaved chains. Structure and properties of bioabsorbable polyglycolide (PGA) and poly (glycolide-co-lactide) (PGA-co-PLA) fibers were investigated during several industrial processing stages and in vitro degradation by means of wide- angle X-raydiffraction In the orientation stage, the PGAfibers were found to have higher degrees of crystallinity than corresponding PGA-co-PLA samples produced under similar conditions. In the hot-stretching and post-annealing stages, after fibers were braided, PGA samples were found to gain more crystallinity and higher T_g than PGA-co-PLA samples. The higher crystallinity in PGA fibers co-cultured in a slower rate of degradation and hot-stretchingstages were released in the post-annealing stage for a1l PGA and PGA-co-PLA samples The typical cleavage-induced crystallization mechanism. Theheat shrinkage in the glass transition area was found to disappear after 6-8 days of degradation for all PGA and PGA-co-PLAsamples, indicating the amorphous portions of the polymers lost orientation after a short period in the buffer solution, mostlikely due to relaxation of the cleaved chains.