Sepsis is a life-threatening organ dysfunction caused by an inappropriate response by the host organism to an infection that causes 5 to 11 million deaths per year. Despite great advances in understanding the pathophysiological processes that lead to the development of this difficult condition, little has changed in the process of diagnosing and treating septic patients. Namely, the best therapy is still considered to be the one that is started on time or as soon as possible after the appearance of suspected sepsis. In doing so, the role of potential markers of sepsis is very important, which we define as any substance, structure or process that can be measured in the body or its products and influence or predict the incidence of outcome or disease. Great efforts have been made in recent decades to find a ubiquitous, reliable, fast and cheap method that will justify doctors' suspicion of sepsis early enough and enable rapid intervention. These methods are expected to be able to confirm or rule out sepsis, assess the severity of the condition and the outcome of the disease, and assist in the application of therapy, primarily antibiotics. So far, over 170 potential markers have been identified, but only some of them have been shown to be useful in clinical practice. The introductory five chapters present the findings to date and provide a context on the severity and magnitude of the global problem we call sepsis. The second part of this paper discusses the use of markers already in everyday clinical use, as well as those used in specific situations such as neonatal sepsis or assessing the development of the immunosuppressive phase of the septic response, and markers whose promising diagnostic and prognostic power still must be fully proven.