The NLM soon became an "international leader in automated services". In 1958 the Director of the library, Dr. Frank B. Rogers, began looking into computer use. While Rogers was investigating computer usage, Winifred Sewell was revising the Medical Subject Headings list in case the NLM adopted a computer-based system. In 1959 the NLM contracted a biomedical computer expert to "investigate the feasibility of using electronic digital computers for publication of the Index Medicus and as a basis for construction of efficient reference and biographic services" .

During the early 1960s, the NLM hired General Electric's Defense Systems Department (Lilley and Trice) to develop a new "method of using computers for composition, storage, and retrieval, and printing services for Index Medicus." This new system was called MEDLARS (Medical Literature Analysis and Retrieval System). The MEDLARS system, which was operational by 1964, produced a printed index and offered specialized subject bibliographies (Bellardo and Bourne).

The MEDLARS system had to meet certain criteria before the NLM would consider using it. The system must be computer-based, and it must have a unit record from which all other output is derived. Finally, the subject headings must be extended beyond the typical two or three headings assigned to each item at the Library of Congress or at the manual NLM system. MEDLARS met all three expectations. Later, MEDLARS was expanded to bring cataloging "into line" and changes were made allowing MEDLARS to become a cataloging and indexing system (Lilley and Trice).

During the late 1960s NLM worked with several different systems in order to learn about the latest online developments. In January 1968, NLM gained access to the CIRCOL system allowing the staff to observe a functioning online system. In October 1968, NLM contracted with SDC to use the ORBIT system to experiment with online systems. NLM also considered installing the SUNY system, but it could not be easily expanded to fit the needs of the NLM without great and expensive modifications.

After viewing and using online systems, the NLM staff wanted to combine its database and telecommunications with an online system, which led to the development of AIM-TWX and ELHILL. NLM decided to use the TWX (Teletypewriter Exchange Network) of AT&T and AIM (Abridged Index Medicus). SDC modified ORBIT II to met the special searching needs of the MEDLARS system. NLM named this retrieval system ELHILL. ELHILL "was the first large-scale online retrieval system to offer the capability to display a thesaurus hierarchy of subject-related search terms, and to allow searchers to incorporate parts or all of the hierarchy into their search strategy" .

In 1970 and 1971, F. Wilfrid Lancaster performed a formal evaluation of the AIM-TWX system in which he hoped to determine the "potential benefits of such a service to users, and to provide empirically-based answers to a range of questions concerning the technical aspects of the system." After concluding this evaluation, Lancaster and the staff at NLM realized that a network like AIM-TWX would work and that a demand for an expanded online system existed. The staff at NLM wanted to reduce the cost of this service and realized that if NLM ran the system it would be less expensive; therefore, the staff began to look into running the system themselves (Bellardo and Bourne).

NLM awarded a contract to the Computer Science Corporation for the technical development of MEDLARS II but later canceled the contract when the performance of the system did not meet NLM's expectations. Later that same year, 1971, Director Martin M. Cummings (NLM), gave SDC the contract to complete the MEDLARS II system. SDC completed its work at the end of 1974 (Lilley and Trice). MEDLARS II used online interactive searching and retrieval capabilities rather than the batch-mode retrieval used in MEDLARS I (Bellardo and Bourne).

In October 1971, the NLM began putting part of the MEDLARS database on its computer in Bethesda, Maryland. After months of hard work, NLM had added to the database, now called MEDLINE, bibliographic records and subject indexing for 1,200 journals, which were worldwide in scope and covered the three most recent years as well as the current year. The MEDLINE system began servicing medical schools, libraries, hospitals, and research institutions in the United States, Canada, England, and France.

Usage of the MEDLINE system grew at such a terrific rate during 1972 that in early 1973 the NLM awarded a contract to SUNY BCN to provide additional online service for its users. As MEDLINE grew, the NLM staff created numerous new databases, including SERLINE, SDILINE, CATLINE, CANCERPROJ, and EPILEPSYLINE (Bellardo and Bourne). In 1972 TOXICON , an online system containing pharmacology and toxicology, was opened to users. The NLM developed MEDLARS III in 1979 (Lilley and Trice).

[Sources: Lilley, D. B. & Trice, R. W. (1989). A history of information science, 1945-1985. San Diego: Academic Press. And Miles, W. D. (1982). A history of the National Library of Medicine. US Department of Health and Human Services: Bethesda, Maryland.]