The effect of duration of acute compression of the spinal cord was assessed in a new model in the rat. The spinal cord was acutely compressed for varying times by a modified aneurysm clip which produced a compression force of 180 grams. The effect of duration of compression was measured by the inclined plane method of assessing the animals' clinical performance. The results showed a linear relationship between log compression time and clinical performance. Thus, the clinical effect of acute compression of the spinal cord injury is inversely related to duration of compression time and the relationship has been precisely quantified. These results suggest that persisting compression should be relieved as soon as possible in order to improve recovery.