The Pennsylvania Union List of Serials is a new project funded by the State Library of Pennsylvania. In 1979 it awarded the Pittsburgh Regional Library Center $99,304 in LSCA Title III funds for first year development of a statewide union list which will be on-line through OCLC. PRLC’s history of working with on-line union lists is reviewed, and plans for the first year are described. Initially, there will be concentration on system design. At the same time, a core list of approximately 2,000 titles will be selected, as will the libraries to participate during 1979–1980. Future plans will consider some decentralization and COM production. All work will be in accordance with national standards and plans. The Pennsylvania Union List of Serials will incorporate the PRLC and University of Pittsburgh on-line union lists, which already have data for more than 50,000 titles and 150,000 holdings on-line. This project should work to bring uniformity and fairness to interlibrary loan lending and borrowing throughout the state.