This protocol will determine serial serum TNF and IL-1 levels in critically ill infants and children with suspected sepsis and correlate these findings with diagnosis and outcome. Of particular interest will be the levels found in patient subpopulations not as yet studied, including neonates and patients with necrotizing enterocolitis, "adult" respiratory distress syndrome, and primary and secondary immunodeficiencies. Information gained from this study will add to the existing knowledge of the role of these mediators in sepsis.