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In this article, nine web based OPACs of state universities’ central libraries in Tehran were evaluated. For this purpose, first a list criteria for the evaluation of OPACs was drawn from the literature and an evaluation checklist was prepared. Then OPACs were evaluated using the checklist. The results showed the need for some improvement in the design of the OPACs. In terms of accessibility and usability of search system, they were relatively good. However, in term of the process of accessing information, user friendliness, presentation of different types of information resources and direct interaction between user and system, they were poor. The findings indicated that little attention had been paid to users' needs in designing the studied OPACs.