A great deal of progress has been made regarding improved prehospital transport, the quality of trauma care, and injury prevention research. The analysis of the four determinants of outcome in the trauma victim allowed for the discovery of subgroups who may benefit from a change in triage, resuscitation, or management. Our recent investigation into the effect of host factors on mortality resulted in the discovery that pre-existing illness predicts outcome independent of other determinants, including age and ISS. This article serves as an introduction to the effect of PED on trauma victims, including prevalence of specific PED, as well as disease-specific treatment considerations. The bottom line in care of any trauma victim is that all deviations from normal must be noted, but they should be evaluated properly with respect to the acute injuries. It is the authors' hope that this overview will guide the intensivist in focusing on the treatment of acute injuries without losing sight of the importance of both recognizing and managing chronic illnesses so their detrimental effect on patient outcome can be minimalized. A large multicenter investigation is needed to see whether these recommendations will, in fact, positively impact on trauma victim outcome.