OBJECTIVE To determine the prognostic value of the biomarkers procalcitonin, interlukin-6 and C-reactive protein in septic patients. METHODS A cohort of 81 septic patients. METHODS Critical Care Unit. Dr. Peset Hospital. Valencia (Spain). METHODS Divided according to sepsis classification (sepsis, severe sepsis and septic shock), source and two different groups (medical and postsurgical). VARIABLES ANALYZED: Quantitative (procalcitonin, interleukin-6, C-reactive protein, lactate, age, Apache II and SOFA scores upon admission and after 3 and 7 days). Qualitative (ICU mortality, multiorgan failure development and sex). METHODS Mann-Whitney U-test for the comparison of quantitative variables, χ² test for qualitative variables. Multivariate analysis with mortality and multiorgan failure as dependent variables and the described quantitative parameters as independent variables. ROC curves of the variables found to be significant in the multivariate analysis. RESULTS Septic shock patients showed greater mortality and more frequent multiorgan failure. Comparison of survivors versus deceased patients showed significant differences in Apache II score, interleukin-6 and lactate (p<0.001) upon admission and after 3 and 7 days. Similar findings applied to the comparison of patients with and without multiorgan failure, and on the same days. Procalcitonin only showed differences on days 3 and 7 (p=0.001). In the multivariate analysis with mortality as dependent variable, interleukin-6 proved significant on day 3 (OR 2.6). With multiorgan failure as dependent variable, only the SOFA score showed significance (OR 2.3). The Apache II and interleukin-6 ROC curves corresponding to day 3 showed areas of 0.80 and 0.86, respectively. CONCLUSIONS 1) Interleukin-6 is an inflammatory biomarker with mortality prognostic value. 2) None of the biomarkers proved predictive of multiorgan failure.