We investigated three subjects with unexplained sensory loss meeting criteria for conversion disorder using brain fMRI during unilateral and bilateral vibrotactile stimulation. In each subject, stimulation of the affected limb did not produce activation of the contralateral primary somatosensory (S1) region, whereas bilateral limb stimulation did. These findings implicate selective alterations in primary sensorimotor cortex activity in conversion disorder, and may also reconcile the discordant results of previous studies.