This essay relates one type of online service, with which I have worked closely, to another type of online service with which I have great familiarity as a user. The first type of online service is represented by the Pennsylvania Union List of Serials (PaULS). It is online through OCLC and gives the holdings for approximately 80,000 titles held by Pennsylvania and area libraries. As I will discuss later, the PaULS database, and other online serial union lists as well, have implications for collection development and collection management.