Biocompatibility of PLLA and stereocomplexed PLA nanofibers was evaluated by subcutaneous implantation in rats for 4-12 weeks. Characterization of the nanofibers was performed by GPC, SEM, wide-angle X-ray diffraction, and optical microscopy of hematoxylin-eosin stained ultrathin sections of explanted nanofibers. Stereocomplexed PLA nanofiber showed slower degradation than PLLA nanofiber and thus retained their shape after prolonged implantation. Furthermore, stereocomplexed PLA nanofiber caused milder inflammatory reaction than PLLA nanofiber. These results offer the potential use of PLLA and stereocomplexed PLA nanofibers as a biomaterial for short-term and long-term tissue regeneration, respectively. Stereocomplexed PLA nanofiber after in vitro degradation showed smaller degree of swelling than PLLA nanofiber. Taking the results of in vivo degradation together with in vitro degradation into consideration, bioabsorption mechanism of the in vivo degradation of the nanofibers is proposed.