Feeding intolerance is a common condition among preterm infants owing to immaturity of the gastrointestinal tract. Clinical symptoms consist of gastric residuals, vomiting, and/or abdominal distention. Feeding intolerance prolongs dependency on parenteral nutrition, which, in turn, is associated with an increased risk of complications (e.g., late-onset sepsis and parenteral nutrition-associated liver disease). In this thesis, we describe a new pharmacotherapy to accelerate intestinal maturation using insulin as trophic factor, thereby reducing feeding intolerance. The natural insulin concentration in human milk declines rapidly in the first three days postpartum, and the insulin concentration in DHM is significantly reduced by heat-dependent pasteurization techniques used in human milk banks. To date, preterm formula does not contain any insulin. Therefore, an rh-insulin formulation has been developed for enteral administration in preterm infants. This thesis shows that enteral administration of two different rh-insulin dosages is safe, and, compared to placebo, significantly reduces time to achieve full enteral feeding in preterm infants with a GA of 26–32 weeks. Implementation of enteral rh-insulin in standard clinical practice may be considered once efficacy and safety have been confirmed in a second planned, adequately powered, randomized controlled trial in preterm infants