As digital libraries move from demonstration projects to the real world of working libraries, it is critical to assess and to document the impact of the shift. This paper reports the methodology and initial results of an Institute for Library and Information Studies (IMLS) funded research study of the operational and economic impact of an academic library's migration to an all-electronic journal collection. Drexel Library's entire print and electronic journal collections and associated staff are the test bed to study three key research questions: (1) What is the impact on library staffing needs? (2) How have library costs been reduced, increased and/or re-allocated? (3) What other library resources have been affected? We are using quantitative and qualitative methods to answer the research questions operationalized in the following tasks: (1) Measure the staff time, subscriptions costs and other costs related to each activity required to acquire and maintain print and electronic journals. (2) Compute the per-volume, per-title, and per-use costs of acquiring and maintaining print and electronic subscriptions. (3) Study all impacted library services, including changes in reference service, document delivery, and instructional programs. Initial results of measuring staff time indicate Information Services and Systems Operation departments constitute the majority of personnel costs for electronic journals. Technical Services and Circulation account for the majority of staff costs for print journals. Per title subscription costs appear to be substantially lower for electronic titles obtained through aggregator collections.