A six-year-old, female Jin-do dog was referred for the recurrence of vaginal prolapse. Less than 7 months previously, the dog with the vaginal prolapse had been treated with homone therapy because ultrasonography had identified a single follicular cyst in the left ovary. Three months after the first visit, the dog came into heat and the vaginal prolapse recurred. Ultrasonography showed multiple follicular cysts in both ovaries and radioimmunoassay detected a plasma estradiol-17beta concentration of 13.3 pg/ml. Treatment involved the repositioning of the vaginal prolapsed, ovariohysterectomy and the resection of the protrunding tissue. The dog had been completely recovered two months later after the treatment. Keywords: follicular cysts, ovariohysterectomy, ultrasonography, vaginal prolapse