The regional registration in 11 prefectures and one area covering 34% of total Japanese population started in 1974, increasing gradually to 21 prefectures and one area in 1993 covering 48.5% of total Japanese populations, by the Japan Trophoblastic Disease Committee under the auspices of Japan Society of Obstetrics and Gynecology. The results showed marked decreasing trend in incidence of molar pregnancy and choriocarcinoma in Japan. The most frequent antecedent pregnancies of choriocarcinoma has shifted from molar pregnancy in 1974 to term pregnancy in 1993. The Choriocarcinoma Risk Score Table that is in use and of practical significance, differentiating choriocarcinoma from invasive or metastatic mole by reference to simple 8 clinical items with the probability of more than 90% when compared with the histological diagnoses, is also presented.