The effect of experimental trauma on the blood flow in the central (essentially gray matter) and peripheral (essentially white matter) regions of the sheep's spinal cord was studied using a radioactive microsphere technique. In seven out of eight animals, a progressive fall in blood flow occurred in both the peripheral and central regions of the cord within 2 hours following injury and remained reduced over the period of recording (up to 12 hours). Changes in local vascular resistance indicated that in approximately 60% of our animals, changes in arterial pressure alone contributed highly significantly to the decreased spinal blood flow. There remains the possibility that early therapeutic intervention could sustain neuronal function where local blood flow would otherwise be inadequate in the damaged spinal cord.