Coherence analysis revealed that the 10-Hz rhythm in sympathetic nerve discharge (SND) was not correlated to that either in inferior olivary activity of decerebrate cats or in neocortical spindles of urethane-anesthetized cats. Also the discharges of some ventrolateral medullary and raphe neurons contained a 10-Hz rhythm that was not correlated to that in SND. These data support the hypothesis that a 10-Hz rhythm reflects the organization of a brainstem network that specifically governs sympathetic outflow.