Healthy and septic human neonates have elevated serum IL-18 levels compared with adults. Using a murine neonatal model of intraabdominal sepsis with systemic (intraperitoneal) IL-18 complementation, Wynn et al. report that IL-18 potentiated mortality in both neonatal sepsis and endotoxemia through the induction of IL-17A, and depended on IL-1 receptor 1 signaling (but not IL-1β). They propose that targeting this IL-18/IL-1/IL-17A axis may improve outcomes for human neonates with sepsis. However, given the important roles of Th17 responses and IL-18 in host defenses, some caution is in order during a potentially microbe-induced septic process in neonates. The important differences in neonatal and adult responses to sepsis highlighted in this paper emphasize the need for further study of the immune responses of neonates.