More and more libraries are providing access to Web resources through OCLC’s Cooperative Online Resource Catalog (CORC) and, by extension, OCLC’s WorldCat database. The ability to use a database to its maximum potential depends upon understanding what a database contains and the guidelines for its construction. This study examines the characteristics of Web resources in CORC in terms of their subject matter, the source of the content, publication patterns, and the units of information chosen for representation in the database. The majority of the 414 resources in the sample belonged to the social sciences. Academic libraries and government agencies contributed more than 90% of the records for resources in the sample. Using the Anglo-American Cataloguing Rules, 2d edition (AACR2) definitions for publication patterns that are part of the upcoming 2002 amendments reveals that nearly half of the sample fell into the category of integrating resources. Identifying units of representation of the resources described was more difficult. Existing definitions for Web units in development are not adequate to describe all of the resources in the sample. In addition, there is wide variability in the units of representation chosen for inclusion by the libraries contributing records, resulting in little predictability in what units of information might be found in the database.