This study was conducted to clarify the effects of surgical orthodontic treatment for malalignment caused by the prolonged retention of deciduous canines in young dogs. Fifty-five dogs with malocclusion or pre-malocclusion were divided into two groups. Group 1 received surgical orthodontic treatment (32 dogs) using modification of Ross [9] and Yamane's [14] method of treating for malalignment due to prolonged retention of deciduotis canine teeth; Group 2 received no treatment (23 dogs). Occurrence of malocclusion 1-3 weeks after treatment of the group receiving surgery was only 3.8%. However, malocclusion was seen in 73.4% of the non-treatment group approximately 2 years after the first examination. Surgical orthodontic treatment was very useful in treating malalignment due to prolonged retention of deciduous canines in young dogs.