The estimated incidence of twin pregnancy consisting of hydatidiform mole and co-existing fetus is one per 22,000-100,000 pregnancies. Most patients with hydatidiform mole and co-existing normal fetus must be cautioned about the potential for risks of malignant change and severe medical complications, such as preeclampsia, hyperthyroidism and antepartum hemorrhage, that may necessitate prompt pregnancy termination. We experienced a case of twin pregnancy with a hydatidiform mole and co-existing fetus in hypogonadotropic hypogonadismal woman who had been treated with gonadotropin for ovulation induction. A brief reviews of related literatures was done.