Severe sepsis and septic shock are frequently encountered conditions in today's hospital environment. The incidence appears to be increasing despite our growing armamentarium of antibiotics and our enhanced knowledge of the pathophysiologic processes at play. The clinical presentation may take a variety of forms, especially in patients at the extremes of age and in the immunocompromised population. A high index of suspicion and prompt institution of appropriate antimicrobial treatment is mandatory for a successful outcome. It is hoped that adoption of uniform definitions will aid in research and in effective communication concerning sepsis and its adverse sequelae.