Presenting electronic resources to users through a federated search engine introduces unique opportunities and challenges to libraries. This article reports on the decision-making tools and processes used for selecting collections of electronic resources by a project team at the University of Arizona (UA) Libraries for the Association of Research Libraries' Scholar's Portal Project. A brief overview of the Scholar's Portal Project is provided, and the approach used at the UA Libraries to implement the federated search engine is detailed. This article also reports on the results of usability testing, interviews, and a user satisfaction survey used to determine the functionality of Scholar's Portal and the search results. (Contains 2 figures and 31 notes.)