Primary ovarian pregnancy is a rare form of ectopic pregnancy that must be demonstrated with use of 4 Spiegelberg criteria. It is usually diagnosed at laparotomy or laparoscopy, although it may resemble a hemorrhagic corpus luteum. Successful conservative management of ovarian pregnancy with methotrexate has been reported only occasionally. This may be partly because of the rarity of this condition and partly because when medical treatment is successful, the patient does not need to undergo laparotomy or laparoscopy, and an occasional ovarian pregnancy may have been diagnosed as a tubal pregnancy. We present a case of ovarian pregnancy (diagnosed at laparotomy) for which initial medical management with methotrexate failed despite favorable prognostic factors. Whether the unusual location (ovary) could have contributed toward treatment failure is unknown.