Background. Sepsis is an important cause of mortality in newborns. However, a single reliable marker is not available for the diagnosis of neonatal late-onset sepsis (NLS). The aim of this study is to evaluate the value of serum amyloid A (SAA) and procalcitonin (PCT) in the diagnosis and follow-up of NLS. Methods. 36 septic and healthy newborns were included in the study. However, SAA, PCT, TNF-alpha, IL-1 beta, and CRP were serially measured on days 0, 4, and 8 in the patients and once in the controls. Tollner's sepsis score (TSS) was calculated for each patient. Results. CRP, PCT, and TNF-alpha levels in septic neonates at each study day were significantly higher than in the controls (P = .001). SAA and IL-1 beta levels did not differ from healthy neonates. The sensitivity and specificity were 86.8% and 97.2% for PCT, 83.3% and 80.6% for TNF-alpha, 75% and 44.4% for SAA on day 0. Conclusion. Present study suggests that CRP seems to be the most helpful indicator and PCT and TNF-alpha may be useful markers for the early diagnosis of NLS. However, SAA, IL-1 beta, and TSS are not reliable markers for the diagnosis and follow-up of NLS. Copyright (C) 2008 Birsen Ucar et al.