ABSTRACT Despite advances in neonatology, necrotizing enterocolitis (NEC) remains the most common GI emergency of premature infants with significant morbidity and mortality. The pathophysiology of NEC is unclear, non- surgical treatments are mainly supportive, and no predictive tests are currently available. In experimental models of NEC, we have shown that bile acids (BA) play a critical role in NEC pathogenesis. Recently, using prospectively collected, serial fecal samples from premature infants, we have shown that infants who develop NEC have significantly higher coefficient of variation of total fecal bile acids (CV-TBA) than matched controls. Importantly, these variations occur well prior of diagnosis. We hypothesize that variation of TBA can predict development of NEC and aim to build and validate predictive models from daily fecal samples collected from the NICUs at Banner University Medical Center - Tucson and Vanderbilt University Medical Center. Successful completion of this proposal could lead to implementation of the first predictive test for this devastating disorder.