The purpose of this study was to examine the inability of paraplegic (P) subjects to redistribute fluid below the spinal cord lesion during arm exercise, with emphasis on the role of the sympathetic system in this redistribution failure. Fifteen male P and 15 male able-bodied [control (C)] subjects performed arm cranking exercise, and volume changes in the calf were measured by strain gauge plethysmography before, during, and after exercise. Muscle pump activity in the legs of C subjects was eliminated. The rate of calf volume decrease at the beginning and halfway points of the exercise period, the total volume decrease during exercise, and the volume increase during recovery were significantly lower in P than in C subjects. Whereas completeness of the lesion had no influence on leg volume changes, the rate of calf volume decrease at the beginning of exercise and the total volume decrease during exercise were significantly correlated with the level of the spinal cord lesion. This study confirms that P subjects are unable to redistribute fluid effectively below the spinal cord injury during arm exercise, which is partly caused by a loss of sympathetically induced vasoconstriction and which appears to be independent of the completeness of the lesion but dependent on its level.