Infections in critically ill patients are more common than in most other parts of the hospital, and are often the most complicated to manage.  Underlying disease and the reasons for admission make the diagnosis, management and prevention of infection challenging. Developments in technology, the treatment of previously untreatable malignancies, complex surgery procedures, and an increasing age profile result in more patients vulnerable to infection and a greater number of patients needing critical care support.   Infections in the Adult Intensive Care Unit is designed to help trainee and practicising physician, surgeon or other medical professional manage the acutely ill patient in the critical care unit, before transfer from the emergency department, or on the hospital ward where effective management may avoid admission to the critical care unit. It has been co-authored by a clinical microbiologist, intensivist and clinical infectious diseases physician to cover some of the major infections presenting in the adult critical care unit.  It provides broad principles to be used based on the latest evidence combined with common sense and the results of many years of combined experience.