A 1.5 year old female intact guinea pig presented to the Cornell Exotic Clinic with a 3 day history of anorexia, lethargy, and expelling bloody tissue from her urogenital tract. Physical examination revealed bilateral abdominal masses caudal to the kidneys and ultrasound examination revealed bilateral ovarian cysts, a diffusely thickened uterus and a mass in the right uterine horn. Cystic ovaries are very common in guinea pigs. The predominant form of ovarian cyst is cystic rete ovarii with 75.9 % of cysts examined. Follicular ovarian cysts are the second most common, with teratomas, parovarian cysts, and cyst of the surface epithelium being much less common. Common therapy includes hormone therapy to lyse the cysts, however the majority of the cysts would be expected to not respond. Ovariohysterectomy is the only definitive cure for cystic ovary disease in guinea pigs, however surgery is challenging, considering anatomy and special anesthetic risks of guinea pigs.