The purpose of this study is to determine how selected
variables affect the usability of the OPAC screen designs in
terms of success rate, search time, and preferences of
users. Tests for OPAC screen usability have been done, but
not many organized and systematic. This research is intended
to help designers and librarians create and/or select the
most useful OPAC screens for undergraduate students in
college or university libraries, and to help them make the
best decisions when faced with a trade-offs between
usability and cost. This study suggests a method for
testing usability of online catalogs in terms of success,
speed, and users' preferences.