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The vascular supply to the human spinal cord has been studied in a series of observations made in the cadaver during routine necropsies performed at the Radcliffe Infirmary, Oxford. In addition to conventional anatomical dissection of the larger vessels concerned, injections with either indian ink or radio-opaque material were made into the spinal vessels. The examination of the larger spinal vessels was aided by X-rays or by rendering the spinal cord transparent with oil of wintergreen. The origin of the spinal vessels was studied and a division suggested between a aubolavian-vertebral supply to the cephalic part of the spinal cord and a direct aortic supply to the more caudal part of the spinal oord. From the evidence of both anatomical and pathological observations, the point of transition between the subolavian-vertebral supply to the direct aortic supply was considered to be in the region of the T1 spinal-cord segment. The anterior radicular tributary arteries to the anterior spinal artery were studied in a series of 40 injected spinal cords. The number of tributaries ranged from 3 to 9 with a mean of 5.6. More tributaries joined the anterior spinal artery from the left (127) than the right (97) side. The largest anterior tributary (the artery of Adamkiewicz) was always found accompanying one of the nerve roots from T7 to L3. It was three times commoner on the left than on the right side and in 12 out of the 40 specimens was accompanying the left T10 spinal nerve root. The anterior spinal artery was confirmed as the most important single vessel and was always found to run longitudinally for the whole length of the spinal cord. The posterior spinal arteries were much smaller and were more irregular vessels than the anterior spinal artery. A good anastomosis between the anterior and posterior spinal arteries was always demonstrable around the conus medullaris and was often seen in the cervical region. This was seen in the arterial infections which, when made into the anterior arterial system, flowed easily into the posterior spinal arteries. The sulcal arteries arose from the anterior spinal artery and passed backwards in the anterior median sulcus. They entered the grey commissure and by turning either left or right supplied the grey matter and central white matter of one side. These vessels and their branches formed the centrifugal arterial system. The centripetal arterial system, of lesser importance, was formed by radial arteries proceeding inwardly as branches from the coronal arterial plexus surrounding the spinal cord. The spinal veins, with some differences, were arranged on the same general plan as the spinal arteries. The differences were that the spinal veins were more numerous and that the anastomoses between large veins were more common. The veins were most prominent on the posterior aspect of the spinal cord and the largest single vessel was usually a single median posterior vein. The pathological observations were made on cases selected for the information they provided on disorders of the human spinal vascular supply. These cases showed that obstruction or disturbance of the spinal cord vessels could occur at different points of the pathway of arterial supply and venous drainage. Aorta. Aortic atherosclerosis and aortic thrombosis were shown to cause a syndrome of chronic ischaemia of the spinal cord. Aortic trauma with mural haematoma caused acute infarction of the spinal cord, a similar sequel to that more commonly seen following spontaneous medial dissection of the aortic wall. Vertebral arteries. Two cases illustrated spinal cord infarction and ischaemia caused by obstruction to both vertebral arteries. This unusual syndrome arose from trauma to the cervical spine causing a tear through one intervertebral disc. The resultant angulation at the point of the intervertebral disc tear kinked and obstructed both vertebral arteries. Interpostal arteries. Surgical damage to an intercostal artery giving rise to an important radicular tributary to the anterior spinal artery was shown to cause extensive infarction of the spinal cord in the territory of the anterior spinal artery. These paired intercostal and lumbar spinal arteries supply the spinal cord below the T1 spinal-cord segment. The majority of these spinal arteries may be obstructed with impunity but when, as in this case, the occluded artery is an intercostal artery giving rise to a major radicular tributary, serious infarction of the spinal cord will be caused. Radicular tributaries. Obstruction to these vessels in the intervertebral foramina was shown to be caused acutely by herpes soster and more gradually in cases of malignant tumour Infiltration. The sequel to this obstruction of the radicular tributaries was a state of haemorrhagic infarction affecting most of the cross-sectional area of the spinal cord and extending through several spinal-cord segments. Anterior spinal artery. Three cases of infarction of the spinal cord due to obstruction of the anterior spinal artery by thrombus were described. In two of these cases the cervical part of the anterior spinal artery was obstructed whilst in the third case the spinal cord below T11 segmental level was affected. In one case there was a relationship between the site of the thrombosis in the anterior spinal artery and the position of cervical spondylotic protrusions which were adjacent to the thrombosed artery. Ho cause for the arterial lesion was found in the other two cases. The longitudinal extent of the infarction in the two cervical cases was similar and its caudal extent was at the T1 segmental level. Below this level the spinal cord was supplied by a radicular tributary to the upper thoracic region and the blood flow was unaffected by the thrombus in the anterior spinal artery above. In its cross-sectional area the infarction always involved the anterior horns and the grey commissure but not the most posterior part of the posterior horns. The white matter of those parts of the anterior and lateral white columns adjacent to the grey matter was also infarcted. The region of infarction was often asymmetrical and might differ markedly at slightly different levels. The asymmetry was considered to be an effect of the various suloal arteries which entered to supply either the left or the right side of the spinal cord. Small spinal vessels. Three cases were selected to describe the effects of disease affecting the small spinal vessels. In one of these cases meningo-vascular syphilis had caused chronic atrophy of the spinal cord affecting both grey and white matter. The spinal vessels showed connective tissue thickening due to former syphilitic arteritis. Another case studied was a case of tuberculous meningitis causing, by arteritis, a severe haemorrhagic infarction of the spinal cord. In this case the subarachnoid space was distended with tuberculous exudate which had caused an endarteritis affecting all the spinal arteries surrounding the spinal cord. The third case considered in this group was a case of sarcoidosis affecting the spinal cord. Sarcoid granulomata were present around small spinal vessels in the leptomeninges and entering the spinal cord along perivascular spaces. In contrast to the effects of syphilis and tuberculosis, the vessels in contact with the sarcoid granulomata were not obstructed and there was no gross infarction evident in the spinal cord. Veins. Five cases of a chronic necrotising spinal cord disorder associated with grossly abnormal spinal vessels were described. The necropsies showed a complicated abnormality of the spinal vessels with large abnormal veins in the caudal and posterior regions of the spinal cord.