Studies are reviewed that examine how perceptual and attentional systems operate in the cortically disconnected human. The data indicate that even though both simple and complex perceptual information associated with the cognitive activities of each disconnected half brain show virtually no interactions, the attentional system remains largely integrated in the split-brain patient. It also appears that the human brain is subject to a set of finite resources it can allocate to cognitive activities. These resources are not changed following cortical disconnection. Taken together, studies to date support the view that the attentional system is an independently functioning and integrated entity, following brain bisection, that participates in both perceptual and cognitive activities of each hemisphere.