Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host's immune response to infection. Sepsis can occur at any age, but the incidence of sepsis is higher in the extreme age groups, including newborns and the elderly. Bacteria are the most common causative agent of sepsis. In the pathogenesis of sepsis, the most significant damage occurs at the level of microcirculation. Sepsis, or systemic inflammatory response syndrome (SIRS), develops when the release of pro-inflammatory factors is greater than required by the condition of inflamed tissues. Such an inflammatory response is considered malignant since it is neither controlled nor regulated. Chills, fever, tachypnea and tachycardia are among the basic clinical symptoms and signs of sepsis. Untreated sepsis or sepsis that does not respond to the applied therapy can progress to multiple organ failure syndrome. Patient has severe sepsis when there is, in addition to sepsis symptoms, hypoperfusion or organ dysfunction present as well. Severe sepsis can progress to septic shock, which means persistent hypotension, despite adequate therapy. Patient monitoring and clinical, laboratory and radiological diagnostics are necessary procedures in the evaluation of a septic patient. Blood culture is considered the most important microbiological examination in proving the causative agent of sepsis. The treatment of a septic patient begins with the intravenous administration of fluids. Antimicrobial treatment must be administered intravenously and should be started immediately after taking blood samples for microbiological analysis. The final outcome depends on the early use of antimicrobial treatment, because late initiation of therapy increases the patient death rate.