From the early 1960s, the US National Library of Medicine (NLM) has been a leader in applying computer technology to accomplish traditional bibliographic and reference functions. medline, in the early 1970s, was the first large-scale online medical bibliographic reference system. That role has been altered by today's Web environment, which has increased the number and extent of NLM services and the audience for them. The NLM has formally declared that it will seek to serve the general public after over a century of serving the library and medical communities exclusively. In the last several years, many new services have been introduced to fulfil this mandate, including medlineplus and ClinicalTrials.gov. Also a part of the NLM's vision for the 21st century is the need to ensure that the proliferating forms of electronic health information-bibliographic, full text, graphic, audiovisual-are captured and preserved for posterity. A national library such as the NLM has as much an archival responsibility for this electronic information as for centuries-old printed and manuscript historical treasures.