A rat model study was performed to evaluate the effects of compression of the thoracic spinal cord. Dorsal screw compression of the thoracic spinal cord up to 50% canal diameter was created at T5 (Group A), T5 and T11 (Group B), and T5 and T8 (Group C). Clinical grading (Tarlov criteria), sensory evoked and motor evoked potentials, horse raddish peroxidase neural transport, and microangiography were studied. Single level compression had little effect. For double compression, there were marked detrimental effects both clinically and electrophysiologically, especially when the compression was close together. Neutral transport was affected in all groups, but the difference was not significant between them.