Teratomas are neoplasms composed of tissue foreign to the area in which it is found. They are considered to be an acquired neo­plastic disease and familial incidence has not been reported. Only one occurrence of teratoma between monozygotic twins has been found in the literature. Here we report the case of two heterozygotic twins with benign cystic teratomas of the ovary as a base for future research for efficacy of an accurate familial follow-up in order to diagnose this neoplasm in early stage and for the molecular understanding of pathogenesis of teratoma.