The presented study is a report of epidemiologic data collected between 1978 and 1980 from patients with gestational trophoblastic disease in the Netherlands. Review of curettings from 344 patients with hydatidiform mole and 33 patients with partial mole resulted in review diagnoses of hydatidiform mole in 283 women, of partial mole in 25 women, and of mere hydropic degeneration in 69 women. Upon review of the initial diagnosis of complete and partial hydatidiform mole, 18% of the cases were considered false-positive. After the evacuation of a molar pregnancy, 10% of the patients needed chemotherapy because of the diagnosis of persistent trophoblastic disease. In patients with a review diagnosis of hydropic degeneration, this was never necessary.