Abstract Necrotizing enterocolitis (NEC) is severe and life-threatening disease of infant gastrointestinal tract (GIT). It is a defect of GIT adaptation to extrauterine life, which affects mostly premature infants and infants afflicted by congenital developmental defects of GIT or heart. Gut barrier disruption and presence of abnormal gut microbiota has eminent role in NEC pathogenesis. Nowadays, the diagnosis of NEC is based on presence of clinical symptoms - abdominal distension, blood in stool and radiologic finding Pneumatosis intestini. However, the symptoms are in early stage of NEC non- specific and do not allow unambiguous distinguishing of NEC from other GIT disorders or sepsis. Aim of this thesis was to extend the understanding of inflammatory response in neonates with NEC and to find applicable biomarker for early diagnosis of NEC and thereby provide quick intervention. Cytokines have important role in immune response regulation. Although the connection between some cytokines and NEC was described, the inflammatory response during NEC was not yet properly stated. The levels of 40 cytokines related to inflammation was shown in this thesis. Intestinal - Fatty Acid Binding Protein (i- FABP) is a small...