The National Library of Medicine (NLM), on the campus of NIH in Bethesda, Maryland, is the world's largest medical library. It collects materials in all major areas of the health sciences and to a lesser degree in such areas as chemistry, physics, botany and zoology. The collections stand at 5 million items--books, journals, technical reports, manuscripts, microfilms, photographs and images. Housed within the Library is one of the world's finest medical history collections of old (pre-1914) and rare medical texts, manuscripts, and incunabula.

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Extensive knowledge base of medical information on symptoms, diagnosis, and misdiagnosis of more than 20,000 medical conditions. Research causes of your symptoms or research treatments for diseases.