In many areas, GTN have become a success story in the field of oncology. It is well known that pregnancies with hydatidiform moles are high risk and carry the potential for the development of malignant forms of GTN. Monitoring with hCG levels has become accepted as the model for a sensitive and specific serum tumor marker. Chemotherapeutic strategies are well documented and are usually successful. However, as the recent literature demonstrates, further basic and clinical research is needed to define the epidemiology of GTN, especially choriocarcinoma resulting from nonmolar gestations. Identification of high-risk patients after evacuation of hydatidiform mole, perhaps using newer hCG subunit assays, might prevent postmolar GTN by identifying patients who would benefit from prophylactic chemotherapy. Because of the high cure rates for nonmetastatic and low-risk metastatic GTN, further research is needed to define cost-effective and efficacious regimens with low toxicity. A uniform system for staging and assessing risk of patients with GTN should be adopted and used by all investigators reporting results of chemotherapy. Although the World Health Organization system is the most widely used prognostic scoring system, further study with large numbers of patients is necessary to validate the weighted scores assigned to each item in the scoring system. Finally, collaborative groups should conduct randomized prospective studies to evaluate newer regimens for high-risk GTN and to develop salvage regimens using rigorously controlled phase II studies.