The aim of this study was to evaluate the blood flow characteristics of the uterine artery and intratumoral vessels in patients with GTD. Twelve patients with GTD were evaluated with TVS, and 11 also had CFD sonography performed. Spectral analysis of both uterine artery and sampled intratumoral and intramyometrial vessels revealed systolic frequencies and PI that were significantly higher in the uterine artery than in sampled intratumoral vessels (P < 0.05). Uterine artery PI correlated significantly with age (P = 0.043), uterine size (P = 0.003), and β-HCG titer (P = 0.03). Intratumoral PI correlated significantly with uterine size (P = 0.05). Intratumoral PI did not correlate with patient age, the shape or orientation of the uterus, presence or absence of subendometrial halo, endometrial thickness or echogenicity, or impression of myometrial invasion. Regression analysis of β-HCG titers on uterine artery and intratumoral PI revealed a linear association. TVS and color flow Doppler sonography are useful in the assessment of patients with GTD. The PI is strongly associated with prognosis and correlates with β-HCG titers.