Probiotics are favorable microorganisms that regulate the flora of the gastrointestinal system and stimulate the immune system. Necrotizing enterocolitis incidence is 10-25% in newborn infants whose birth weights are < 1500 g. Although bifidobacterium and other lactobacilli spp. have been used to reduce the incidence of necrotizing enterocolitis in clinical trials, Lactobacillus reuteri has not been used in the prevention of necrotizing enterocolitis in very low birth weight infants yet. The objective of this study is to evaluate the efficacy of orally administered Lactobacillus reuteri in reducing the incidence and severity of necrotizing enterocolitis in very low birth weight infants.