The anatomy, neurophysiology, semiology, and pathology of the pupillary reflexes are reviewed. Recent advances in the demonstration of midbrain pathways projecting to and from the Edinger-Westphal (EW) nucleus are discussed. Observations of the pupillary diameter and reflexes in premature infants can be helpful in the diagnosis of neurological disorders. A relative afferent pupillary defect (RAPD) without visual disturbances can be suggestive of midbrain lesions. Automated pupil perimetry is proposed as an objective method for the evaluation of the visual field. Tonic pupil, the pupil in diabetics, and blue-cone monochromatism are also discussed.