The serious disorders of nervous function which may result from central protrusions of the intervertebral disc are exemplified in the thoracic region of the spine where this type of prolapse has acquired -a sinister reputation, and the few cases treated by operation that have so far been reported bear witness to the severe damage that these protrusions inflict on the spinal cord and to the grave hazards attending their surgical removal. Thus, of Muller's (1951) four cases, three were left after operation with a complete or almost complete transection of the cord, and the fourth after a slight temporary improvement also developed a total paraplegia. Of Hawk's (1936) three patients who survived operation, all with severe pre-operative spinal cord damage, one was made worse by, and the other two showed no benefit from, surgery. Mixter and Barr (1934) reported three cases, two of which developed a total transverse lesion and the third eventually showed slight improvement. So of 10 cases of central thoracic disc prolapse treated surgically, six were left with virtually complete cord transection and there was little or no worthwhile improvement in the other four, a unique morbidity rate among benign compression lesions of the cord. It is my purpose to describe a series of 11 cases all proven by operation which does to some extent confirm this grave picture, but also reveals that it is possible to make an accurate pre-operative diagnosis of this type of hemiation and to remove a certain number of these protruding discs not only without further damage to the spinal cord but with almost complete restitution of neurological function.