Neglect is a disorder of orienting in which patients are unaware of objects in their contralesional visual field. Yet their pre-attentive vision is still able to parse the scene to segregate figure from ground, group objects, and to define their primary axis. Therefore, it appears that perceptual processing may be intact up to the level of semantic classification, and that neglect only acts at the level of selection for action and access to awareness. Several mechanisms contribute to neglect, including disinhibited orienting to the ipsilesional field, a deranged representation of space, and deficits in disengaging attention, oculomotor corollary discharge, and representation of contralesional movement trajectories. Recent studies have begun to identify the neural substrates involved in these mechanisms.