The Research Libraries Group proposes to establish a cooperative development program with the Library of Congress to provide computer-based, on-line access by library networks to the machine readable MARC file at the Library of Congress and data bases elsewhere. This document provides the proposal for Phase One, which would establish a communications link between members of the Research Libraries Group and the Library of Congress to test currently available data base access methods and provide empirical data for planning later phases. This phase is presented in terms of development, including economic considerations, benefits and technical approach; products; the project plan; personnel; and budget. Phases Two and Three are briefly described for better understanding of the role of Phase One in the total project. (Author/KP)