Duplicate serial titles are often the object of cancellation as libraries trim collections due to budget constraints and rising journal prices. Duplicate tide cancellation has been a noted trend as libraries look for the most costeffective way to stretch (heir limited budgets. This study compares duplicate serial use at two departmental science libraries, the Chemistry Library and the Physics/Astronomy Library, at the University of Illinois at UrbanaChampaign (UIUC). Cost per use was determined for all serials in both libraries during a three-month swey of journal use. Results indicate that because of heavy use. most duplicate journals are cost effective subscriptions at both locations.