22 dogs (31 eyes) that had treated with trimedioprim-sulfamethoxazole for tear staining syndrome at Snoopy Pet Clinic from October 2000 to September 2002 were reviewed. Of the 22 dogs, 12 were female and 10 male. Their mean (± SD) age was 3.5 (± 1.3) years. The breeds of the dogs consisted of Maltese (8 dogs), Shih tzu (6 dogs), Poodle (5 dogs), Yorkshire terrier (2 dogs), and Mixed (1 dog). The dogs received 30 mg/kg trimethoprim-sulfamethoxazole perorally twice daily for two to six weeks. 26 (19 dogs) of the 31 eyes (22 dogs) recovered completely and did not show relapse at 26-30 weeks after treatment. Any complications did not observed. Five eyes of three dogs were not cured. Two eyes (one dogs) of them had not response to medicament and three eyes (two dogs) recurrence but the clinical signs decreased. It was considered that the trimethoprim-sulfamethoxazole was effective for the treatment in dogs with tear staining syndrome.