Non-Hodgkin's lymphomas arising in the spinal cord are extremely rare. Only eight single case reports have been well confirmed in the literature. Herein we describe a 59-year-old woman with symptoms attributable to a spinal cord lesion. Physical examination revealed neurologic deficits but no evidence of tumor elsewhere. Although several imaging studies were performed, only magnetic resonance imaging with use of gadolinium revealed the exact site and extent of the lesion. Laminectomy and direct examination of the spinal cord disclosed a discolored region at the level of the 11th thoracic vertebra. A biopsy specimen was obtained, and pathologic examination revealed an intermediate grade, mixed cell lymphoma of T-cell origin. Radiotherapy was administered to the lesion and adjacent region of the spinal cord with use of 6-MV photons and an anteroposterior-posteroanterior technique; the total dose was 45 Gy in 23 fractions. No chemotherapy was given. After 3 years of follow-up, the neurologic signs and symptoms were stable, and repeated magnetic resonance imaging with use of gadolinium showed no residual tumor. In addition to the case report, we review the literature on primary lymphomas of the central nervous system and discuss treatment recommendations.