Programs of the National Library of Medicine over almost a century and a half are described, ranging from a history of American medical literature and the development of medical indexing to modern technological developments. Activities covered include the development of the Toxicology Information Program and the online data base TOXLINE; the traditional library services which are now modernized through CATLINE (Cataloging-On-Line), MEDLINE, SERLINE, and DOCLINE (Document Delivery On-Line); the responsibilities of the History of Medicine Division, a collection of pre-1870 manuscripts, prints, and photographs; the extramaural programs of the library, including health sciences library construction, the Regional Medical Library system, research grants, training programs, and publications; acquisition of non-U.S. biomedical literature and relationships with institutions abroad; the services of the National Audiovisual Center including AVLINE (Audiovisuals On-Line); new technological applications such as biomedical communication, computer based education, and computer research and development; and the administrative structure of the library. (JAB)