Since the 1960's, the number of publications has increased at a phenomenal rate, and the introduction of the computer has resulted in greatly expanded technological advances in information processing and information access. The information delivery component of health sciences libraries has been transformed; and concomitantly, their interorganizational relations have been altered. This research investigates the impact of a federally mandated information program. The Medical Library Assistance Act was passed in 1965 to support the escalating information needs of health professionals. Also, a computerized access system for biomedical literature was introduced by the National Library of Medicine. This study focuses on health sciences libraries in the Pacific Northwest, primarily Oregon and Washington, from 1965 to 1985 to determine how the Act impacted them. Of the various theories in interorganizational relations, Raelin's legal-political model provides the most cogent framework. One of his two types of mandated networks results from society-at-large placing its will on a group of organizations through the enactment of a law. As a decision maker with a mandate, the National Library of Medicine has changed the relationships of health sciences libraries through a hierarchical network, the Regional Medical Library Program. This analysis is a combination of quantitative and qualitative methods and personal observation. Data were collected to determine the number of interlibrary loan transactions routed through the Regional Medical Library at the University of Washington and consortium grants from the National Library of Medicine. A survey of health sciences librarians in the Pacific Northwest was conducted to find out to which organizations they belonged, their familiarity with the Medical Library Assistance Act, and their first use of MEDLINE. The results show that interorganizational relations among health sciences libraries in the Pacific Northwest increased after passage of the Medical Library Assistance Act of 1965. The confluence of the establishment of the Regional Medical Library network with the development of a computerized database, MEDLINE, made this component of the Medical Library Assistance Act a resounding success. Information technology also changed a hierarchical structure to a more lateral one, whereby health sciences librarians at all levels perform their own on-line database searching.