There is a report of a case of a bilateral ovarian cancer in a 51-years old woman whose monocygotic twin sister had died of the same carcinoma one year before. In both cases it was partly a solid partly an adenocarcinoma of the ovaries. According to general statistics of carcinoma here it is an accidental event. Developmental aspects allow us to think of a common genetic disposition. The question is whether in case of a carcinoma of the ovaries in a monocygotic twin the adnectomia in the twin sister should be done.