Most ovarian leiomyomas arise in premenopausal women. They originate from hilar smooth muscle, smooth muscle of blood vessels, or smooth muscle metaplasia of ovarian stroma. They are usually discovered incidentally. Gross and microscopic features are similar to those arising in the uterus. Rare cases may be associated with Meigs' syndrome, peritoneal leiomyomatosis, and intravenous leiomyomatosis.