Helicopter emergency medical services (HEMS) and its possible association with outcomes improvement continues to be a subject of debate. As is the case with other scientific endeavors, debate over HEMS usefulness should be framed around an evidence-based assessment of the relevant literature. In an effort to facilitate the academic pursuit of assessment of HEMS utility, in late 2000 the National Association of EMS Physicians' Air Medical Committee prepared annotated bibliographies of the HEMS-related outcomes literature. As a result of that work, two review articles-one covering HEMS use in nontrauma and the other in trauma-published in 2002 in Prehospital Emergency Care surveyed HEMS outcomes-related literature published between 1980 and mid-2000. Given the broad interest in the earlier reviews, and the increasing rate of publication of HEMS studies, the current project was executed with the intent of updating the annotated HEMS outcomes-related bibliography, covering a three-year time interval (through 2003) since the prior reviews.