The current study investigates the clinical characteristics of patients with partial molar pregnancy who developed persistent gestational trophoblastic tumor (GTT). Between January 1979 and January 1989, 16 of 240 (6.6%) patients, who were followed for partial mole, developed persistent GTT. Fifteen (94%) patients were diagnosed as having a missed abortion before evacuation and only 1 patient presented with excessive uterine size and theca lutein ovarian cysts and was felt to have molar disease. No patient presented with toxemia, hyperemesis, or hyperthyroidism. All 16 patients developed nonmetastatic GTT. Fifteen patients achieved complete remission with methotrexate-citrovorum factor and only 1 patient required combination chemotherapy to attain remission. None of the patients had histologic evidence of choriocarcinoma. Patients with partial mole who developed persistent GTT did not have clinical or pathological characteristics that distinguished them from other patients with partial mole. All patients with partial mole should be followed with measurement of hCG levels to assure gonadotropin remission.