Trauma and exposure to toxic and infectious agents invariably lead to organ damage followed by significant morbidity and mortality. Although these conditions have typically been associated with the battlefield, today they are more prevalent in urban areas. The events of September 11,2001 have brought this problem to the forefront of national and international concern. The demand for solutions is justifiably high, and the research community needs to adjust its efforts appropriately. Combat Medicine is meant to be a concise manual for the young clinical or basic investigator who is studying organ injury following trauma or toxic or infectious assaults either in an urban or battlefield setting, with an emphasis on current research issues in emergency and military medicine. The aim of Combat Medicine is to inspire surgical and medical residents and fellows, as well as biology and biochemistry students and fellows, to pursue research careers in the fields of military, trauma, and emergency medicine. Combat Medicine is not intended to be an exhaustive review; rather it is an introduction to key principles of this field.