OBJECTIVE: This study describes MR imaging of eight patients with endometrial stromal sarcoma and correlates the imaging findings with histopathologic findings. To our knowledge, the radiologic findings of this entity have not been reported in the literature. CONCLUSION: Endometrial stromal sarcoma typically presents with extensive myometrial involvement, which is either sharply demarcated or diffusely infiltrative. Bands of low signal intensity are observed within the areas of myometrial involvement on T2-weighted images. These bands correspond to the preserved bundles of myometrium on pathologic examination. Tumor extension along the vessels or ligaments is another characteristic of MR imaging of endometrial stromal sarcoma.