The reuse and secondary analysis of digital data in the environmental and social sciences is aided greatly by well-established data repositories and a research culture that fosters trusted data sharing, respectively. However, relatively few studies in either of these disciplines have considered the component activities of reusing data beyond an initial phase of discovery; more often, studies have identified barriers to access or focused on the need to properly attribute datasets. We present a comparative analysis of those activities and practices surrounding secondary use of publicly available data in the environmental and social sciences. Identified activities in these two disciplines are grounded in the current literature, which include: selection criteria for reuse, methodological approaches as they vary by discipline, transfer protocols, citation practices, and explicit barriers to access and use of secondary data. This comparison of data practices provides a formalization of the implicit activities surrounding reuse that will prove highly valuable to data librarians and data scientists in their interactions with an increasingly interdisciplinary and collaborative research community. An analysis of data reuse also offers much needed insight to the development and maintenance of deployed cyberinfrastructures, particularly as these large-scale systems are geared toward data-centric research.