OBJECTIVE To examine the behavior of interleukin-6 (IL-6) and procalcitonin (PCT) and verify whether they can be used to differentiate children with septic conditions. METHODS Septic children aged between 28 days and 14 years, prospectively enrolled from 01/2004 to 12/2005, were divided into sepsis (SG; n=47) and septic shock (SSG; n=43) groups. IL-6 and PCT were measured at admission (T0) and 12h later (T12h). PCT results were classed as: 0.5 ng/mL=sepsis unlikely; > or =0.5 to <2=sepsis possible; > or =2 to <10=systemic inflammation; > or =10=septic shock. RESULTS Ninety children were included. At T0, there was a higher frequency of SSG with higher PCT compared with SG [SSG: 30 (69.7%)>SG: 14 (29.8%); p<0.05]. Similar results were observed at T12h. PRISM was significantly higher for SSG patients with higher PCT than SG patients. At T0, IL-6 levels were higher in SSG [SSG: 213.10 (10.85-396.70)>SG: 63.21 (0.86-409.82); p=0.001], but not statistically different at T12h. IL-6 levels positively correlated with PRISM score in SSG patients at admission (p=0.001; r=0.86). CONCLUSIONS PCT and IL-6 appear to be helpful in early assessment of pediatric sepsis, are of diagnostic value at admission, and are related to disease severity.