Background. An accessory ovary is an uncommon congenital anomaly of the female reproductive tract. Tumors arising in ectopic ovaries are extremely rare. Case. This 18-year-old woman had a pelvic tumor attached to the right ovary which was solid cystic and lobulated and histologically and immunohistochemically showed the appearances of sclerosing stromal tumor, a benign entity. Conclusion. We present the first reported case of sclerosing stromal tumor that arose in an accessory ovary. (C) 2001 Academic Press.812318319