The majority of what we know about the development of the absorptive process is derived from animal studies, studies in human fetal or stillborn tissues, and epidemiologic investigations derived from clinical experience. One can readily ascertain from this review that the absorption of nutrients in the intestine of the premature infant relates to a dynamic developmental process in which the consecutive stages are pre-programmed but can also be regulated by environmental factors. An understanding of these factors may lead to therapeutic intervention in premature infants, as has been the case for the developing lung and respiratory distress syndrome. Application of this knowledge to the critically ill premature infant in the intensive care unit will need to proceed cautiously, but it is likely to yield major benefits in terms of decreased short- and long-term morbidity in these highly vulnerable patients.