Sepsis is a serious high mortality disease. As regards pathophysiology, it is a systemic inflammatory response to infection. Its timely diagnosis strongly influences mortality. The identification of biomarkers is used for diagnosing, monitoring, and prognosis in septic patients. The methods for their measurement cover a range of disciplines such as clinical biochemistry, haematology, immunology, and clinical microbiology. The most frequently used sepsis markers in routine clinical diagnostics are C-reactive protein and procalcitonin. The detection of selected cytokines, mediators, and surface markers in immunocompetent cells gives us further chance for improvement of this diagnostics. The methods of calculating gene expression represent a technology with a potential for the discovery of new biomarkers which would improve both diagnostics and therapy in the sense of personalized medicine.