The virtual Canadian union catalog (vCuc) project is a project among Canadian libraries to use Z39.50 (an information protocol standard) for searching distributed individual library catalogs and union catalogs. This paper summarizes the major technical, vendor, bibliographic data, and administrative issues that must be resolved before the distributed catalog environment will be able to provide the functionality which is available with a centralized union catalog. Solutions and the parties who are responsible for implementing them (librarians, vendors, national libraries and library organizations, library customers, or a combination) are identified. Issues discussed include: retrieval of locations and holdings information; the variety of attributes supported by vendors; inconsistency in vendor and library mapping of use attributes; ability to link from client system to other applications; merging result records of multiple systems; non-standardized use of library symbols; searches for specific serials issues; item level data and need for linkage of circulation and bibliographic records; incomplete cataloging; search terms supported by library; placement of location information and ease of user retrieval; description of Z39.50 features and options available in target system; and charging for the service. Vendors, technical developers, and librarians must continue to work together to find solutions which will assist libraries in providing service to their clients. (SWC)