Plasma and cerebrospinal fluid catecholamines were measured in three patients with multiple sclerosis who had dorsal column stimulators placed at the T5-7 levels. Stimulation for 3 minutes and 20 minutes increased release of plasma norepinephrine, epinephrine, and dopamine, as well as norepinephrine into the cerebrospinal fluid. Neither dopamine nor epinephrine was released into the spinal fluid during or after stimulation. Percutaneous stimulation did not release catecholamines into the plasma or spnal fluid, suggesting that these findings were not simply related to sensory stimulation or stress. Plasma catecholamine levels were inconsistently correlated with pulse rate changes during and after stimulation but not with blood pressure, although the changes in pulse rate and blood pressure were relatively small compared to changes in plasma catecholamines. This study suggests that plasma catecholamines and spinal fluid norepinephrine reflect central activation of sympathetic nervous system pathways and are more reliable indicators of sympathetic activity than changes in cardiovascular function.