In 2004, an ad hoc committee was charged with preparing this third report examining the most senior ST appointments to federal government positions and updating the accompanying list of the most urgent ST presidential appointments. Sufficient changes have occurred since the National Academies 2000 report on presidential appointmentsincluding the 2001 terrorist attacks, the anthrax deaths, the reorganization of homeland-security activities in the federal government, new developments in ST, and concerns about the politicization of ST decision making and adviceto warrant this new edition. In contrast with previous reports on the subject, this one covers not only presidential appointments to top ST leadership positions but also the appointment of scientists, engineers, and health professionals to serve on federal advisory committees that focus on science-based policy or on the review of research proposals. The committee recognizes that other areas of federal responsibility are as important as ST, but ST appointments are the only ones within its purview.