We tested the hypothesis that tinnitus was due to excessive spontaneous activity in the central auditory system by seeking cerebral blood flow (CBF) changes that paralleled changes in the loudness of tinnitus in patients able to alter the loudness of their tinnitus. We found CBF changes in the left temporal lobe in patients with right ear tinnitus, in contrast to bilateral temporal lobe activity associated with stimulation of the right ear. The tones activated more extensive portions of the brain in patients than controls. We conclude that tinnitus is not cochlear in origin and associated with plastic transformations of the central auditory system. We suggest that tinnitus arises as a consequence of these aberrant new pathways and may be the auditory system analog to phantom limb sensations in amputees.