Ovarian stromal hyperthecosis is characterized by diffuse distribution of luteinized stromal cells accompanied by varying degrees of stromal hyperplasia. We report a case of ovarian stromal hyperthecosis with particular regard to magnetic resonance (MR)-pathologic correlation. At initial MR imaging, the central areas of the bilateral ovarian masses showed hypointensity on T1-weighted images and hyperintensity on T2-weighted images, while the peripheries of the bilateral masses showed isointensity to myometrium on T1-weighted images and heterogeneous signal intensities on T2-weighted images. At 15 days after the initial MR imaging examination, a second MR imaging demonstrated shrinkage of the bilateral ovarian masses. Change in the peripheries to predominantly isointensity to myometrium on the T2-weighted images was also observed. The patient underwent bilateral oophorectomy. Microscopic examination revealed scattered nests of lutein cells on a background of densely proliferated ovarian stroma with minimal collagen production in both ovaries. Edema was occasionally seen in the outer portion but was marked in the central zone of the ovaries, particularly on the left. The final pathologic diagnosis was stromal hyperthecosis. With regard to MR-pathologic correlation, the MR findings in the peripheries of the bilateral masses (isointensity relative to myometrium on both T1- and T2-weighted imaging) showed the characteristics of stromal hyperthecosis.