Twin gestations consisting of a complete hydatidiform mole and coexisting fetus are rare and associated with an increased risk of persistent gestational trophoblastic tumor. Data were abstracted from 25 well-documented cases from the literature to which we added an additional case. Cases were then separated according to whether the pregnancy was evacuated before fetal viability (19 cases) or resulted in a surviving infant (7 cases). The previable and viable groups did not differ with respect to mean age, gravidity, parity, presenting symptoms, accuracy of sonographic diagnosis in identifying the molar component, uterine size at evacuation, or the presence of preeclampsia and theca lutein cysts. Statistically significant differences (P < .05) were detected between the previable and viable groups in estimated gestational age at evacuation (18.6 weeks vs. 33.0 weeks), the discrepancy between uterine size and estimated gestational age at evacuation (8.1 weeks vs. 1.0 weeks), and preevacuation serum hCG level (1,078,416 vs. 167,883 mIU/liter). Persistent GTT developed in 68.4 percent of the previable group patients and 28.6 percent of those in the viable group (P = .09). In patients with complete hydatidiform mole and coexistent fetus, fetal survival is associated with clinical characteristics suggestive of less exuberant molar growth. The advanced gestational age required to produce a viable, surviving fetus is not an independent risk factor for the development of persistent GTT.