Tumors of the canine reproductive tract are uncommon and represent somewhere between 2.4% to 3% of all canine tumors. Of these reproductive tumors, the vast majority are tumors of the vulva and vagina and a smaller percent are ovarian or arising from the uterus or cervix. Tumors of the mammary gland are not included in these numbers, and although important, will not be discussed in this paper. Approximately 86% of all tumors of the vulva and vagina are benign leiomyomas. This is a case report of a 12 year old Shetland Sheepdog with a vaginal leiomyoma. The bitch presented with a perianal mass, among other clinical signs. The mass was removed surgically and histologically diagnosed as leiomyoma. Three months later she was doing very well with no occurrence of clinical signs. The purpose of this paper is to discuss differential diagnoses for vaginal masses and to concentrate on the incidence, biological nature, clinical signs, treatment and prognosis of vaginal leiomyomas.