Two cases of thoracic level paraplegia after lumbar spinal surgery were retrospectively reviewed after 1 year of follow-up. Charts and perioperative records were reviewed in an effort to determine the possible etiology of this rare and devastating complication. We were unable to find any reports in the English-language literature regarding thoracic-level paraplegia in an isolated lumbar procedure (in the absence of preexisting structural instability or thoracic level lesion). We found 23 reported cases of acute spontaneous paraplegia or quadriplegia from fibrocartilaginous (disk) emboli to the spinal cord. This was a retrospective review specifically seeking possible predisposing conditions, intra- or postoperative hypotension, or technical errors that might have led to the complication of paraplegia. No preoperative thoracic level intracanal lesions were identified. There were no episodes of profound hypotension noted perioperatively. The specific pattern of paralysis found in these two patients did not correlate with the level of the surgery performed. Both patients had findings consistent with cord edema and spinal cord infarct in the thoracic region. We believe that these two cases represent acute spinal cord infarcts in the "watershed" region of the thoracic cord, the exact cause of which could not be determined. A theory of an embolic phenomenon is proposed as a possible etiology.