Certain infectious diseases have a higher frequency and severity in patients with diabetes mellitus (DM), which substantially increases morbidity and mortality rates. DM acts as a predisposing factor for bacteremia seen in both the nosocomial and community settings. The greater incidence of infections in diabetics is caused by the accompanying hyperglycemia, which generate an immune dysfunction characterized by disorders of the neutrophilic granulocytes, diminished antioxidant activity and humoral immunity. Other complications of DM such as micro or macroangiopathy, neuropathy, urinary and gastrointestinal motility disorders, among others, contribute to the pathogenesis of infectious processes in these patients. It is thought that cross-linking of advanced glycation end products is associated with inactivation of immune components, contributing to a higher vulnerability to infections. An association between hyperglycemia and infection in critically ill patients has been proposed; however, evidence remains limited. Several risk factors infl uence negatively in the prognosis of severe sepsis, such as advanced age, immunosuppression and chronic alcoholism. There still is contradictory data concerning the impact that DM could exert on the prognosis of septic patients.