This study was undertaken to characterize 20 cases of dominance aggression seen at Tufts University School of Veterinary Medicine and to investigate the efficacy of our non-confrontational behavior modification program for 8 weeks. The 20 cases included 18 pure breed and 2 mixed breed dogs. Thirteen of the dogs were male. The dogs' ages ranged from 7 to 84 months (mean 32.1 +/- 22.64 SE). There was no correlation between the severity of dominance aggression and the signalment of the dogs. At the conclusion of the eight week follow up period, 14 dogs (70%) were reported to have responded to the treatment to some degree. Six dogs did not demonstrate any noticeable reduction in aggressive behavior or became more aggressive. The results of the study is powerful evidence of the efficacy of the non-confrontational behavior modification program.