Sonograms of 27 patients with gestational trophoblastic disease were evaluated and categorized to newer concepts regarding the pathology and pathogenesis of this disorder. The patients were assigned to the following subgroups: 1) classical or complete mole; 2) partial or incomplete mole; 3) coexistent mole and fetus; 4) hydropic degeneration of the placenta; 5) locally invasive mole; and 6) metastatic trophoblastic disease, including choriocarcinoma. The utility of this categorization and of ultrasound in the diagnosis and subsequent management of these patients is presented.