Objectives: This study evaluated the action of low level laser therapy (LLLT) on the percentage of newly formed bone in rabbit mandibles that underwent distraction osteogenesis (DO). Study design: Ten rabbits underwent bone lengthening according to the following protocol: Latency ? 3 days; Activation ? 7 days 0.7 mm/d; and Consolidation ? 10 days. The control group was composed of 4 rabbits. The experimental group, composed of 6 rabbits, received infrared GaAlAs LLLT (?=830 nm, P=40 mW) according to the following protocol: point dose of 10 J/cm2 applied directly on the bone site that underwent DO during bone consolidation at 48-hour intervals. Results: The percentage of newly formed bone was greater in the LLLT group (57.89%) than in the control group (46.75%) (p=0.006). Conclusion: The results suggest that LLLT had a positive effect on the percentage of newly formed bone. Betterquality bone sites may allow early removal of the osteogenic distractors, thus shortening total treatment time.