The aim of this study was to assess histologically the effect of LLLT (lambda 830 nm) on the repair of standardized bone defects on the femur of Wistar albinus rats which were grafted with inorganic bovine bone Gen-ox(R). Three randomized groups were studied: group I (control, n=6); group II (Gen-ox, n=9) and group III (Gen-ox + LLLT, n=9). The animals were irradiated every 48 h during 15 days; the first irradiation was performed immediately after the procedure. The animals were irradiated transcutaneuosly at four points around the defect. At each point a dose of 4 J/cm(2) was given (Ø approximately 0.6 mm, 40 mW) and the total dose per session was 16 J/cm(2). The animals were killed by an overdose of general anesthetic 15, 21 and 30 days after surgery. The specimens were routinely processed by embedding in paraffin, serially cut and stained with H&E and Picrosirius and analyzed under light microscopy. The results showed evidence of a more advanced repair in the irradiated group when compared to the non-irradiated groups. The repair of the irradiated group was characterized by both increased bone formation and amount of collagen fibers around the graft within the cavity from the 15th day after surgery, also considering the osteoconductive capacity of the Gen-ox. We conclude that LLLT had a positive effect on the repair of bone defects implanted with inorganic bovine bone.