Following the world's first successful laser emission by Maiman in 1960. Laser technology was first applied to medicine in 1961 for the photocoagulation of detached retinal lesions. Since then, lasers have been used in a variety of clinical fields including selective resection and vaporization of tumor tissues, lithotripsy, vascular anastomosis, irradiation of local infectious agents, pain and inflammation control, photostimulation of nerve fibers and local blood circulation. Clinical applications of lasers are largely divided into thermodestructive therapy and nonthermal phototherapy . The former, generally referred to as high reactive-level laser treatment (HLLT), uses laser-generated heat to obliterate target tissues. On the other hand, the latter low reactive-level laser treatment (LLLT) is based on biostimulation or bioactivation by laser light, although the mechanism of bioactivation by LLLT has not been clearly understood. In veterinary medicine, HLLT has been used for the surgical resection of tumors since the 1980s, while LLLT has become clinically applicable since the early 1990s for pain relief, inflammatory control and rehabilitation in various surgical and orthopedic disorders, especially wound healing, hip dysplasia, patellar luxation, spondylosis deformans, osteoarthritis, intervertebral disc herniation, bone fracture, contusion and other types of luxation. In this report, we conducted a double-blind trail of LLLT in 100dogs with orthopedic conditions to examine the clinical significance of laser phototherapy.