Official website of the National Institutes of Health (NIH). NIH is one of the world's foremost medical research centers. An agency of the U.S. Department of Health and Human Services, the NIH is the Federal focal point for health research. The NIH website offers health information for the public as well as medical professionals. The website has an A-Z index on various health topics, NIH health resources, clinical trials, health hotlines, MEDLINEplus, drug information, and more.