Although osteochondromas are among the most common benign tumors of bone, they rarely compress the spinal cord or cauda equina. We describe a case in which a solitary sacral osteochondroma compressed the cauda equina, producing sensory disturbance and urinary dysfunction. The tumor was removed via lumbar hemilaminectomy. The pertinent literature is discussed, as well as the diagnostic features of plain x-ray, computed tomography, and magnetic resonance imaging.