A popular starting point for libraries engaging in research data management (RDM) services is a needs assessment (NA); a preliminary count identified more than 50 published NA case studies. However, no overarching analysis has yet been conducted. The authors compared assessments to characterize the case study institution types; establish the target population assessed; discover cross-institutional trends both in the topics covered and the issues identified; and determine remaining gaps in the literature. Thirty-seven studies conducted in the United States were included. Twenty-five were at public, doctoral, highest-research institutions. The most frequently assessed respondents were faculty (n = 3,847). The most frequent topics involved storing, sharing, and maintaining long-term access to data. Gaps include assessing students, staff, and nonfaculty researcher needs; determining needs at various sized and degree-granting institutions; and investigating RDM needs for non-STEM disciplines.