The Pittsburgh Regional Library Center Serials Cancellation Project originated as a result of substantial cuts in serial subscriptions by many libraries in western Pennsylvania in 1980. To make cancellation decisions and yet retain as broadly based a serials collection as possible in the region, the libraries attempted to communicate with each other in traditional nonmachine ways. Under development at the same time, the Pennsylvania Union List of Serials, a large, widely available database of bibliographic and holdings records, seemed to have the potential to communicate cancellation decisions as they occurred. This article reviews the history of the Serials Cancellation Project conducted by the Pittsburgh Regional Library Center with a grant from the Council on Library Resources. Technical details for implementing the project via the OCLC database are discussed and the findings of the project summarized. It was concluded that the use of large-scale online databases such as union lists of serials offers considerable potential to aid collection development officers and library managers.