A 13-yr-old female nulliparous Allen's swamp monkey (Allenopitchecus nigroviridis) presented with intermittent excessive vaginal bleeding, cyclical lethargy, and a history of irregular menstrual cycles. Abdominal ultrasonography revealed a subjectively thickened, irregular endometrium, multiple leiomyomata (uterine fibroids), and bilateral anechoic foci on the ovaries. Treatment was initiated with leuprolide acetate i.m. monthly for 6 mo. Recheck ultrasound at 3 mo showed a decrease in leiomyoma diameter and no evidence of active follicles on the ovaries. Eleven months following completion of treatment, clinical signs recurred and the animal was treated with a deslorelin implant. Since implant placement, no vaginal bleeding has been noted.