The proposal is aimed at identifying genetic factors that determine the incidence and severity of, and the outcome from life−threatening infections (severe sepsis/septic shock) in patients admitted to High Dependency Units (HDUs) or Intensive Care Units (ICUs) with pneumonia which developed outside the hospital (community acquired pneumonia − CAP) or contamination of the abdominal cavity with faeces due to a leak in the bowel (faecal peritonitis). This will require the acquisition of a large, high quality resource of genetic material (DNA), plasma, urine, white blood cells and clinical information from well characterized groups of similar patients with, or at risk for, severe sepsis/septic shock. The principal objective is to perform studies which are sufficiently large to establish beyond doubt the influence of a series of selected "candidate" genes on the development, progress and outcome of sepsis.