Duplex ultrasonography for persistent gestational trophoblastic tumor. Duplex ultrasonography was performed on 17 consecutive patients being evaluated for persistent gestational trophoblastic tumor (GTT). All patients had had a prior molar pregnancy evacuated and presented with a rise or plateau in their beta-human chorionic gonadotropin levels. The ultrasonography was considered to be abnormal if the image demonstrated a focal area of altered echogenicity within the uterus or if Doppler scanning revealed a focal area of detectable intrauterine blood flow. The ultrasound findings were compared with the pathologic results from dilation and curettage specimens. Ten of the 17 patients had pathologically proven macroscopic tumor. Of those 10, 7 had an abnormal sonographic image (sensitivity, 70%), and 9 had an abnormal Doppler examination (sensitivity, 90%). In all 10 patients the image and/or Doppler examination was abnormal. Among four patients with microscopic disease, imaging was positive in one case, and the Doppler examination was positive in three. Imaging and Doppler ultrasonography are complementary modalities that can reliably detect persistent uterine GTT, and Doppler ultrasonography appears to be more sensitive than imaging in making this diagnosis. 