This study comprised 13 cases having canine perianal adenoma at Veterinary Medical T~aching Hospital, Seoul National University from January 2000 to October 2003. All referred dogs were intact male and mean age of dogs was 11.5 years (ranged from 7 to 15 years). The most prevalent breed was Shih Tzu. The clinical signs were presence of 1 to 5 cm in diameter firm mass, perianal swelling, hemorrhage, pain and dyschezia. The masses were located either in the perineum (12 cases) or tail (5 cases). Five dogs had masses with ulceration. Concurrent prostatomegaly and seminoma was found in 5 and 1, respectively. Castration was performed in 5 cases. In 8 cases, surgical excision of the tumor was performed with castration. There was no recurrence in all cases after removal. In all cases with castration, perianal adenomas were regressed within 1-2 months. In one case among them, excision of the tumor was also performed because of persistent ulceration. According to these clinical results, perianal adenoma excellently responded to castration with or without surgical excision of the tumor.