Near-Earth objects (NEOs) are bodies that orbit the Sun and approach or cross the orbit of the Earth, thus having the potential to collide with it. The possible scale of NEO impacts was brought home to many by the discovery of the Chicxulub Crater lying under Mexico's Yucatan Peninsula and the adjacent sea, believed to have been formed by the impact of a 10-km-diameter NEO some 65 million years ago and linked to the mass extinctions at the end of the Cretaceous Period. Large numbers of NEOs of significant size have now been identified, allowing quantitative assessment of the impact hazard. In 2008 the National Research Council, the operating arm of the National Academies of Sciences, was asked by the US government to “address issues in the detection of potentially hazardous NEOs and approaches to mitigating identified hazards.” An ad hoc committee was set up for this task, chaired by Irwin I. Shapiro, Harvard-Smithsonian Center for Astrophysics. The committee issued an interim report in 2009 and a final report, Defending Planet Earth: Near-Earth-Object Surveys and Hazard Mitigation Strategies, this year. Some passages from this final report, discussing current assessments of impact risks, likely warning times before impact in which to attempt to deflect the NEO trajectory, and the relative magnitude of mortality risks from NEOs in comparison to more familiar causes of death, are reprinted below. On this last, the annual risk of death from NEO impact is found to be an order of magnitude greater than that from shark attack but three orders less than from earthquakes. The reprinted sections are taken from Chapter 2: Risk Analysis, pp. 13–14, 19–20, and 25–27. Copyright © National Academy of Sciences. A PDF of the full report can be downloaded from «http://www.nap.edu/catalog/12842.html».