Adhesion molecules may play a role in the evolution and severity of neonatal sepsis. The purposes of this study were to determine whether serum soluble intercellular adhesion molecule (ICAM)-1, vascular cell adhesion molecule (VCAM)-1, L-selectin, and P-selectin levels are useful tools in the diagnosis of proven sepsis in newborn infants, and whether their levels are related to the clinical severity of the disease. A cohort of 25 consecutive newborns meeting criteria for clinical sepsis, 10 hemoculture-negative (HC - ) and 15 hemoculture-positive (HC + ), were prospectively followed and compared with 12 healthy newborns (six </= 38 weeks of gestational age and six >/= 39 weeks). Serum soluble (s)ICAM-1, sVCAM-1, sL-selectin, and sP-selectin concentrations were measured at the time of the septic workup, then followed by up to three determinations in each newborn every third day. The Score for Neonatal Acute Physiology (SNAP)-II severity was assessed at the moment of highest clinical severity of the disease. At the beginning of sepsis, sICAM-1 levels increased in both groups, being higher in HC + sepsis than in HC - ; sVCAM-1 only increased slightly in HC + sepsis. Soluble ICAM-1 levels were independently related to group of sepsis, and not to days of life. The best initial sICAM-1 cutoff level for diagnosing HC + neonatal sepsis was 274 microg/L. The highest sICAM-1 levels were positively correlated with SNAP-II scores. Soluble L-selectin and sP-selectin did not change. Soluble ICAM-1 levels increased in HC - and HC + sepsis, but concentrations > 274 microg/L suggest HC + sepsis. These levels were related to the clinical severity of the disease. Soluble VCAM-1 levels increased only slightly in HC + sepsis. Soluble L-selectin and sP-selectin did not change.