The institutional review board (IRB) is one part of the research enterprise designated to protect human subjects. At times the IRB can feel like an oppressive oversight body bound by regulations and designed to inhibit research. However, in reality the IRB was an attempt by the federal government to streamline a variety of processes to ensure the protection of human subjects. Growing out of a history of unethical scientific research, the principle goal of the IRB is to protect human subjects. At some institutions the IRB has an additional role, to take a second look at proposed scientific methods to ensure the highest quality research. The legal basis, purpose, composition, and function of an IRB, and potential challenges in human-subjects research are reviewed here.