Evidence is given of the location in man of the fibres going to the sympathetic neurons of the lateral horn that supply the intrinsic and extrinsic muscles of the eye and the sweat glands of the head and neck. For the region of the pons and medulla, the evidence is abstracted from the literature. For the cervical spinal cord, the evidence is from our cases of anterolateral cordotomy. In the medulla, thrombosis of the artery of the fossette latérale destroys the fibres; this locates the fibres in the posterolateral retro-olivary area. But not all fibres to the sudomotor neurons lie there: some run elsewhere, though they probably remain ipsilateral. In the cervical cord, the fibres supplying the sympathetic neurons of the intrinsic and extrinsic muscles of the eye run near the posterior angle of the anterior horn. Most of the fibres supplying the sudomotor neurons lie in the same region, though some lie outside this area but on the same side of the cord.