When discrepant stimuli are presented to each eye and fusion is impossible, perception spontaneously oscillates between the two patterns (binocular rivalry). Functional MRI (fMRI) research identified a frontoparietal network in the right hemisphere associated with perceptual transitions, and it has been proposed that this network is at the origin of the perceptual alternations. Neuroimaging results, however, do not imply causality and lesion studies are needed. Here, we studied one patient who had most of the prefrontal cortex disconnected from the rest of the brain after a bilateral frontal leucotomy. His performance in two binocular rivalry tasks was indistinguishable from that of the controls. The results indicate that prefrontal cortex is unnecessary for perceptual alternations during binocular rivalry.