Due to the immaturity of the digestive system and gastrointestinal motility the preterm infants have a critical challenge in establishing adequate enteral nutrition, which is a frequent cause of gastrointestinal complications such as food intolerance and necrotizing enterocolitis. Modern clinical methods of assessing the maturity of the intestines and the child's readiness for enteral nutrition are subjective, this slows down the expansion of enteral nutrition, increases the duration of parenteral nutrition, and accordingly , period of a child`s hospitalizing. Objective methods of diagnosis are needed, which would contribute to the effective diagnosis and monitoring of food intolerance in preterm infants. Therefore, the purpose of our review was to search and summarize literature data on objective methods of diagnosing impaired food tolerance in premature baby, which could to provide daily monitoring, would be safe, cost-effective and easily accessible. Results and their discussion. Accordingly, three leading and most promising methods of examining the newborns gastrointestinal tract were analyzed. The were ultrasound examination (absence or reverse diastolic blood flow in the umbilical artery, high pulsation index in the fetal venous duct, indicators of blood flow in the upper mesenteric artery of the newborn), near-infrared spectroscopy (estimation of oxygen saturation of splanchnic tissue), and auscultation of intestinal sounds (phonoenterogram). Each of these methods has advantages and disadvantages, but to solve these existing problems, there has been recently an increasing amount of research on the bowel sounds using (namely their computerized assessment) as a new diagnostic tool. New research and further study of intestinal murmurs in premature newborns of different gestational ages with the development of clear criteria for data interpretation are needed to assess the maturity of the gastrointestinal tract, to create a diagnosis plan of food intolerance, and to develop an algorithm for early intervention.