Background. Ovarium cancer is the fifth most common cause of cancer- related death in women and is the most common fatal gynecologic malignancy. So far, ovarium carcinoma has not been reported to have occurred in female- to-male transsexuals. Objective and method. We report on two such cases. Long-term exposure to increased levels of endogenous and exogenous androgens is hypothesized to constitute an additional risk factor in transsexuals as it has been associated with ovarian epithelian cancer. Conclusion. Simultaneous salpingo-oophorectomy should be performed in any female-to-male transsexual undergoing hysterectomy in the course of gender-confirming therapy. (C) 2000 Academic Press.