The Subject Access Research Project was initiated by OCLC in August 1979 to study the process of subject searching in the library catalog, with the objective of identifying features for an automated subject retrieval system which would support the present search tactics employed by library users performing manual subject searches at the library catalog. Subject searchers' spoken thoughts (i.e., protocols) were recorded as they performed their subject searches at varied libraries. An analysis of protocols resulted in construction of a subject searching process model. Features suggested by the model are recommended for implementation in an online public access catalog (OPAC), which has the potential to support new subject-searching features. An OPAC in which the searcher's model of the information retrieval process of traditional catalog searching is implemented may have the same potential as the library catalog, but inclusion of a user-oriented interface is necessary to make it as powerful. An OPAC with such an interface and enhanced with features not previously available to library catalog searchers would actually be more powerful than the traditional catalog. This report includes 39 figures, 27 tables and a 29-item reference list as well as appendices including data collection instruments. (Author/LMM)