Among 26 dogs greater than or equal to 10 years old, the most frequent owner complaints relating to behavioral problems were destructive behavior in the house (n = 10), inappropriate urination or defecation in the house (n = 10), and excessive vocalization (n = 7). The most frequent behavioral diagnoses were separation anxiety (n = 13) and breakdown of housetraining (n = 6). Most of the behavioral problems in the 26 dogs began after the dogs reached the age of 10 years, and most of the dogs had been owned for many years without having behavioral problems. Few behavioral problems in old dogs had a medical basis. Most cases of inappropriate urination or defecation in the house were not related to urinary or fecal incontinence, but were exacerbated by problems such as degenerative joint disease and renal disease. Behavioral therapy is appropriate for behavioral problems in old dogs, and, taking into account an old dog's health and physical limitations, techniques used are the same as for younger dogs.