The National Institutes of Health (NIH) comprise the largest single source of funding in the world for the support of biomedical research. Much of the work of the NIH focuses on the elucidation of fundamental biophysical, biochemical, and biologic aspects of the molecular, cellular, and tissue processes underlying both healthy and diseased states of biologic systems and on the development of cures for the latter. In 2000, the National Institute of Biomedical Imaging and Bioengineering (NIBIB) was created with a somewhat different focus: Rather than concentration on a specific organ system or category of disease, the primary objective of the NIBIB is the advancement of technologies and tools that contribute to all aspects of biomedical research and health care delivery, especially in the imaging sciences and bioengineering. This article provides an overview of the ways in which NIH funds research, with an emphasis on NIBIB support of biomedical imaging. It is intended for radiologists, radiation oncologists, medical physicists, and other readers of this journal, especially those with limited experience in the complex process of obtaining NIH grant support.