Scotopic retinal function undergoes age-related changes early in human infancy. Electroretinographic psychophysical, and pupillographic responses have been used in the study of normal development. Various components of the electroretinographic responses index distal and proximal retinal function. Changes in pupillary diameter, measurable in infants under carefully selected conditions, represent rhodopsin regeneration in the infants under carefully selected conditions, represent rhodopsin regeneration in the photoreceptor outer segment. From psychophysical data, inferences can be drawn about scotopic retinal control of visual performance. These data constrain theories about the determinants of sensitivity, about the flow of signals from the distal, rhodopsin-bearing, outer segments to the proximal retina, and about modulations of straight-through flow by feedback or inhibitory circuits. The results indicate that the post natal development of human scotopic function is due mainly to reorganization of processes central to the photoreceptors.