Anomalies of the lumbosacral nerve roots, in which conjoined nerve roots are most common, are occasionally accompanied by herniated nucleus pulposus. Most of these anomalies were incidental findings from operations, and recent advances in diagnostic imaging techniques have increased the number of cases of lumbosacral root anomalies reported. All these anomalies are congenital, unilateral and almost exclusively situated at the L5-S1 segment. Diagnostic techniques, such as myelography, CT and MRI detect conjoined nerve root. Conjoined nerve root may be confused with a dumbbell tumor or extruded free disc fragment on CT scans. Surrounded by high-signal intensity epidural fat, a conjoined nerve root is more clearly depicted on MR images than on CT scans. Although the size of disc herniation was small, the symptom was magnified by a relatively fixed conjoined root. At surgery, it is necessary for a larger surgical exposure by means of hemi-laminectomy because of the fixation of the nerve roots, and difficulty in retraction. Recently, we experienced two cases of conjoined nerve root and presented them with a review of the literature.