How users meet infrastructure is a key practical, methodological challenge for digital library design. This article presents research conducted by the Social Science Team of the federally funded Digital Libraries Initiative (DLI) project at the University of Illinois. Data were collected from potential and actual users of the DLI testbed—containing the full text of journal articles—through focus groups, interviews and observations, usability testing, user registration and transaction logging, and user surveys. Basic results on nature and extent of testbed use are presented, followed by a discussion of three analytical foci relating to digital library use as a process of assemblage: document disaggregation and reaggregation; information convergence; and the manner in which users confront new genres and technical barriers in information systems. The article also highlights several important methodological and conceptual issues that frame research on social aspects of digital library use.