This article reviews the literature and presents data from our laboratories on sensory deprivation stress and supplemental stimulation of the rat pup and the preterm neonate. The data suggest that the effects of maternal deprivation in the rat pup (suppression of growth hormone release and protein synthesis) are regulated by a specific form of tactile stimulation: only brush stroking of maternally deprived rat pups returned growth parameters to normal; other forms of stimulation, including kinesthetic and vestibular stimulation, were ineffective in restoring normal functions. Other data are presented demonstrating that very small preterm neonates given tactile-kinesthetic stimulation gain more weight per day, spend more time awake and active, and show more mature habituation, orientation, motor, and range of state behaviors on the Brazelton assessment.