The objective of this study is to determine the plasma concentrations and diagnostic accuracy of interleukin-6 (IL-6) and interleukin-8 (IL-8) in newborn infection. One hundred and one newborn infants with clinical signs of infection during their primary hospitalization were investigated with the minimum of a blood culture, C-reactive protein (CRP), full blood examination (FBE), and cytokine concentrations (IL-6 and IL-8). Infection in infants was classified without knowledge of cytokine levels into four groups-definite (n = 11), probable (n = 12), uncertain (n = 52), and nil (n = 26). The median concentrations of IL-6 and IL-8 were significantly higher in the definitely infected group compared with the other three groups (p 175 pg/mL) and IL-8 (>28 pg/mL) had similar sensitivities (80 and 82%, respectively) and specificities (91 and 81%, respectively). Cut-off concentrations could be identified with improved sensitivities (90% for IL-6 and 100% for IL-8) that maintained specificity >50%. However, the confidence intervals were wide for all sensitivities and specificities. IL-6 and IL-8 had little diagnostic accuracy in infants with probable infection. IL-6 and IL-8 concentrations increase early in newborn infants with definite infection.