Despite great advancement in the understanding of the pathophysiology and in the development of novel therapeutic approaches, mortality of sepsis still remains unacceptably high. Adequate laboratory diagnostics represents a major requirement for the improvement of this situation. For a better understanding of the immunological dysregulation in this disease, several markers are now available for routine diagnostics in the clinical laboratory. They include the cytokines interleukin (IL) -6, IL-8, procalcitonin and the LPSbinding protein (LBP). These novel markers will be compared to the conventional procedure of diagnosing inflammatory and infectious disease, such as measurements of C-reactive protein (CRP) as a major acute phase protein and differential blood counting. Important questions addressed in this review are the usefulness of these markers for early diagnosis, their role as prognostic markers and in the risk assessment of patients. Furthermore, we will discuss whether these parameters are to differentiate between systemic inflammatory response syndrome (SIRS) and sepsis at its different degrees. In the case of an infectious nature of the disease, it is important to differentiate between viral or bacterial origin and to monitor the responsiveness of antibiotic therapies. The literature was analysed with focus on the evidence for diagnostic and analytical performance. For this purpose international definition and staging criteria were used in context of criteria for assay performance including sensitivity, specificity, negative and positive predictive values, ROC analysis and other analytical criteria.