While a number of kinds of evaluation/research studies may be conducted during the design and development of a digital library (e.g., usability testing), this module is concerned with methods for evaluating the outcomes, impacts, or benefits of a digital library, including cost/benefit analyses. It also includes methods that are useful for general user studies (i.e., studies that intend to more fully understand people's interactions with digital libraries). While some methods covered here are useful for usability testing, usability inspections and usability testing are explicitly covered in module 6-d, Interaction Design, Information Summarization and Visualization, and Usability Assessment.