Appropriate diagnostic procedure for spinal epidural hematomas has not been established yet. The authors reported a case of spontaneous epidural hematomas at the thoracic level, in which correct diagnosis was made with MRI and good results were obtained by surgery. A 63-year-old female experienced a severe back pain which appeared suddenly during a walk and was followed by motor weakness in both legs deteriorating quickly to paraplegia. The patient had no history of hypertension, trauma or bleeding tendency. The laboratory data were normal. On admission, neurological examination revealed flaccid paraplegia, total sensory loss below the level of Th 6 and urinary and fecal incontinence. Myelograms showed incomplete block at the Th 6 level and postmyelographic CT scan showed an isodense mass, which was suspected to be an epidural tumor located behind the spinal cord. Emergent MRI confirmed an epidural hematoma as a high intensity area extending from Th 3 through Th 11. Sixty-five hours after onset, laminectomy of Th 4 through Th 11 and the evacuation of epidural hematoma were performed without identification of the origin of the bleeding. Neither vascular malformation nor tumor was recognized during operation. Neither was it noticed on histological examination. The patient made favorable progress after the surgery. During the first two weeks in the postoperative period, she regained muscle strength enough to do standing exercise, and satisfactory improvement was made in sensory function including urination and defecation. We emphasize that MRI is indispensable to make a differential diagnosis of thoracic lesions. In the reported case, a correct diagnosis was made with MRI, and an extremely good result was obtained by an emergency operation.