From November 1981 to April 1983, OCLC's Office of Research has been conducting research into online public access catalogs (OPACs). This project has been funded in part by the Council on Library Resources, Inc. as an attempt to provide new insight into the use of online catalogs by obtaining information which may serve as input for better system design of OPACs, utilizing not only desired user features but also more effective searching.The overall study is concerned with the patron and the system and consists of three major parts. The first is the study of current use of online catalogs, i.e., the actual use - what is really happening. The second element is concerned with the perceived patron use of the catalogs and involves the use of questionnaires and focus group interviews at the participating institutions. The third part is an application of the findings from the first two parts.This paper focuses on the current utilization of OPACs. The methodology chosen to employ is to obtain machine-readable transaction logs, via tapes, from the online catalogs and subsequently analyzing these transactions by stochastic search pattern development and mathematical models utilizing Markov chain analysis and the development of transition probability matrices.