To find the most suitable laser for fracture bio-modulation, seventy-five rats were subjected to experimental tibia diaphysial osteotomies then fixed with intramedullary pins. The rats were then exposed to either IR laser or red laser. The rats were divided into three equal groups. Group1 served as control group and left without laser exposure, group 2 and 3 were treated by infrared laser 1064nm and Red laser 650nm respectively. The dose was adjusted to 10 J/Cm2 on daily basis for one week. Fracture healing was evaluated by x-ray on weekly basis for one month.