End-user interfaces for the online public access catalogs (OPACs) of OhioLINK, a system linking major university and research libraries in Ohio, and its 16 member libraries, accessible through the Internet, are compared and evaluated from the user-oriented perspective. A common, systematic framework was used for the scientific observation of the OPAC system's functional capabilities and interface characteristics. Particular emphasis was given to the mode of interaction and user assistance provided. The observations were made over about a 2-week period in 1992. Interface design alternatives were identified and analyzed qualitatively. The 17 OPACs studied used only 6 different software packages, but provided very different interfaces for the same software, as well as a variety of interaction modes. Suggestions are given for the future development of the OhioLINK system to increase ease of use. Appendixes provide examples of output formats and help screens. (Contains 17 references.) (SLD)