The purpose of this study is to evaluate the MR findings of gestational trophoblastic tumors (GTTs). Ten patients who confirmed the diagnosis (4 choriocarcinomas and 6 invasive moles) constituted the basis of our study. The MR findings from these patients were prospectively correlated with the histopathology of resected tumor specimens. MR findings of 4 patients with choriocarcinomas were well-defined, hemorrhagic masses with central necrosis. In contrast, 6 patients with invasive moles showed ill-defined, permeative masses with densely enhanced solid components and tiny cystic lesions. The trophoblastic proliferation, coagulation necrosis, and molar villi had varying signal intensities on T1- and T2-weighted images. Our results suggest that MR imaging is a promising tool for noninvasive morphologic analysis of GTTs.