Introduction: The objective of this review is to give an overview of literature on the survival benefits of Helicopter Emergency Medical Services (HEMS). The included studies were assessed by study design and statistical methodology. Methods: A literature search was performed in the National Library of Medicine's Medline database, extending from 1985 until April 2007. Manuscripts had to be written in English and describe effects of HEMS on survival expressed in number of lives saved. Moreover, analysis had to be performed using adequate adjustment for differences in case-mix. Results: Sixteen publications met the inclusion criteria. All indicated that HEMS assistance contributed to increased survival: Between 1.1 and 12.1 additional survivors were recorded for every 100 HEMS uses. A combination of four reliable studies shows overall mortality reduction of 2.7 additional lives saved per 100 HEMS deployments. Conclusion: Literature shows a clear positive effect on survival associated with HEMS assistance. Efforts should be made to promote consistent methodology, including uniform outcome parameters, in order to provide sufficient scientific evidence to conclude the ongoing debate about the beneficial effects of HEMS.