The absorption, biocompatibility, and fixation properties of self-reinforced (SR) poly-L-lactic acid (PLLA) and poly-DL-lactic acid (PDLLA) were investigated in cancellous bone in 56 rats. Osteotomies of the distal femur were operatively fixed with cylindrical implants made of SR-PLLA and SR-PDLLA/PLLA (40 PDLLA:60 PLLA). The follow-up times were one, three, six, 12, 24, 36, and 48 weeks. Roentgenographic, microradiographic, histologic, histomorphometric, and oxytetracycline-labeling studies were done. Histologically, there was no evidence of inflammation or foreign-body reaction in the bony tissues. Histomorphometric analysis showed that absorption in the SR-PDLLA/PLLA implant was faster than in the SR-PLLA implant. Absorption started peripherally in the implants and continued with subsequent replacement by new bone. At 48 weeks the implant was completely surrounded by a layer of new bone. The SR-PLLA and SR-PDLLA/PLLA implants were visible in all specimens during the 48-week follow-up period. Ninety-five percent of the osteotomies were consolidated. Implants made of SR polylactic acid in rats proved to be biocompatible and slowly absorbable, and they possessed sufficient mechanical properties for fixation of osteotomies.