The posterior parietal cortex plays an important role in visual-spatial attention. Imaging studies reveal consistent parietal activation in attention tasks, while lesions to this area produce significant perceptual deficits. Non-human primate models have been particularly informative in investigating the neurophysiology of attention. The activity of posterior parietal neurons to the same operant stimuli is modulated by whether they are attended or not based on prior information, or whether they attract attention by virtue of their saliency. Posterior parietal neuronal activity appears to provide critical information for shifting attention between stimuli and spatial locations.