Four experiments assessed the relative contribution of oral and nutritional stimuli in the control of suckling in 20- and 25-day-old Sprague-Dawley CD rat pups. Oral factors were critical to suckling satiety, since the initiation of a suckling bout in weanling pups was not retarded by food infused directly into the stomach. As late as 20 days of age, suckling deprivation induced suckling largely through its stimulus-deprivation effects (olfactory, gustatory, somesthetic, and proprioceptive sensations) rather than through its food-deprivation effects. By 25 days of age, the type of oral stimulation that led to suckling satiety expanded; oral stimulation provided by independent feeding acquired characteristics that allowed it also to inhibit suckling. This developmental change in the stimuli that modulated suckling did not appear to be critically dependent on sensory changes in the dam or experiential events within the litter. The behavioral change, therefore, may represent a maturation of neural systems that facilitate the transition from suckling to independent feeding. (38 ref) (PsycINFO Database Record (c) 2006 APA, all rights reserved). © 1980 American Psychological Association.