Uterine morphology assessed by transvaginal ultrasound and the hemodynamics of intratumoral vessels assessed by color Doppler ultrasound were prospectively correlated with the clinical outcome of 25 patients with trophoblastic tumors. Twenty patients were followed without treatment (observation group) and 16 achieved complete local resolution. The four subjects with local persistence were combined with five patients referred from other institutions and received chemotherapy (treatment group). In the observation group both techniques had 100% accuracy in predicting local resolution or local persistence. Persistence was predicted 1-3 weeks before the increase of beta-human chorionic gonadotropin (beta-hCG) levels, whereas resolution was observed up to 8 weeks before the disappearance of beta-hCG. In one patient normal uterine morphology and vascularization in the presence of elevated hCG levels was associated with extrauterine spread. In the treatment group, normal uterine ultrasound morphology and negative color Doppler results had 100% negative predictive value. False-positive results were observed in two cases. We conclude that ultrasound evidence of abnormal uterine morphology or persistent vascularization on color Doppler examination with persistent hCG levels is indicative of local persistence. Normal uterine morphology with negative color Doppler results may be associated with extrauterine spread.