The Association of Research Libraries' (ARL) E-Metrics Project is an ongoing effort to develop new measures that describe and measure networked electronic resources and also to underscore the need for measuring the value of such resources. This article presents results from an ongoing iterative qualitative study with the following goals: (a) to understand ARL libraries' needs for evaluating electronic resources; (b) to refine proposed definitions for describing and measuring electronic resources; (c) to institutionalize data collection for ongoing, annual reporting purposes; and (d) to develop reliable indicators for summative evaluation of electronic resources. Qualitative data collected from participants attending the initial meeting to develop the E-Metrics Project in 2000 are analyzed and compared with an ongoing analysis of interview data collected from the 2003-4 E-metrics participants. The evolving nature of the formats, methods of access, and acquisition plans for electronic resources present challenges in describing and measuring them. New methodologies that use a mixed-methods approach should also evolve to support creative and innovative ways for evaluating an increasingly complex information environment.