In vivo and in vitro studies were performed over the past 6 years to evaluate the short- and long-term biocompatibility, absorbability, strength, and efficacy of polylactic acid (PLA) as a suitable material for an internal fixation system of bone, consisting of a plate and screws. The study was conducted on 30 dogs that underwent osteotomy of the radius and three dogs that underwent osteotomy of the femur. Bone fragments were fixed by the PLA plate and screws. In all specimens, the osteotomy healed in the usual length of time. The dogs were killed after 12 weeks to 4 years. At the time of death, specimens were obtained for mechanical testing and histological analysis. It appears that PLA is biocompatible, is of adequate strength, and has a suitable absorption pattern in the canine model in which it was tested. PLA did not interfere with the process of bone healing and was completely absorbed 4 years after implantation.