Fifteen cadaveric dissections have been performed to determine the anatomic relationships of nucleotomy guide wires. All the 44 guide wires inserted were found to be in contact with at least one nerve root (eight transfixed a root). Guide wires passing anterior to the nerve roots always passed anterior to the center of the disc. Lateral displacement of the skin entry point made safe entry to the center of the disc impossible. Nerve root transfixion is likely to be a significant complication in percutaneous nucleotomy. Entry to the center of the disc avoiding the nerve roots is simplest if the skin entry is as near to the midline as possible.