The purpose of this study was to investigate if early samples of interleukin-6 (IL-6) could distinguish early bacterial sepsis from respiratory diseases in the newborn. IL-6 and C-reactive protein (CRP) were measured at onset of symptoms in newborns evaluated for sepsis during the first week of life. Five groups of children were investigated: proven sepsis, clinical sepsis, respiratory distress syndrome (RDS), transient tachypnoea of the newborn (TTN) and controls. IL-6 was also analysed at the time when CRP was at its maximum level. The results showed that initial IL-6 distinguished proven and clinical sepsis from TTN, but not from RDS. Initial CRP was of no value for diagnosis. Our conclusion is that early IL-6 makes it possible to avoid antibiotics in children with TTN and contributes to the diagnosis of sepsis faster than CRP.