The preweaning development of the pituitary-adrenal system was investigated in perinatally malnourished rodents. Malnourished pups that were routinely handled displayed an earlier plasma corticosterone stress response to electric shock and an accelerated development of feedback inhibition of the stress response by exogenously elevated steroid levels. Although malnourished pups displayed elevated basal corticosterone levels compared to well-fed controls, the post-stress levels were also higher in these malnourished young. Thus, the corticosterone response to stress was not impaired in malnourished pups. The influence of the early handling of malnourished young on pituitary-adrenal activity was also studied. Whereas the accelerated development of the stress response and the elevated post-shock levels were not the result of early handling, the elevated basal corticosterone levels displayed by handled malnourished pups were not present in nonhandled malnourished pups. Thus, the early non-nutritional environment interacts with malnutrition to alter the development of the pituitary-adrenal system.