Spontaneous regression of herniated nucleus pulposus has not been previously documented. Reported here are 11 patients in whom there was unequivocal regression or disappearance of a herniated lumbar disk on follow-up CT study. Two patients with herniated disks were without symptoms. In the nine patients with symptoms, those attributed to the original herniation disappeared or were diminished in all cases. The mechanism of regression of a disk herniation is unknown. Whether or not regression of herniated disk is a frequent occurrence in patients who recover with conservative therapy should be investigated by more frequent use of follow-up CT scans.