OBJECTIVE Necrotizing enterocolitis (NEC) with multiple organ dysfunction syndrome (MODS) carries significant morbidity and mortality. There is extensive experimental evidence to support investigation of therapeutic hypothermia in infants with these conditions. We aimed to establish the feasibility and safety of mild hypothermia in preterm neonates with NEC and MODS as a prelude to a randomized trial. METHODS This was a prospective, nonrandomized pilot study of 15 preterm infants who were referred for surgical intervention of advanced NEC and failure of at least 3 organs. Whole-body cooling was achieved by ambient temperature adjustment with or without cooling mattress. Three groups (n = 5 per group) were cooled to core temperatures of 35.5 degrees C (+/-0.5 degrees C), 34.5 degrees C, and 33.5 degrees C, respectively, for 48 hours before rewarming to 37 degrees C. Infants were carefully assessed to identify adverse effects that potentially were related to cooling and rewarming. A noncooled group (n = 10) with advanced surgical NEC and MODS was used for comparison. Data are medians (interquartile range). RESULTS Gestational age at birth was 27 weeks (26-30), admission weight was 1.1 kg (1.0-1.7), and admission age was 31 days (12-45). Core temperature was maintained within target range for 90% (88%-97%) of the intended time. Statistically significant relationships were identified between core temperature and heart rate (P < .0001), pH (P < .0001), base excess (P = .003), and blood clot dynamics (longer time to initial clot formation, slower rate of clot formation, and decrease in clot strength; all P < .001) as assessed by thromboelastography. No major clinical problems or adverse events were noted during cooling or rewarming. Comparison with the noncooled group revealed no increase in mortality, bleeding, infection, or need for inotropes in infants who were cooled. CONCLUSIONS Mild hypothermia for 48 hours in preterm neonates with severe NEC seems both feasible and safe. Additional investigation of the efficacy of this therapeutic intervention in this population is warranted.