This paper proposes explaining institutional repositories (IRs) and open access, discussing the relationship of open access to IRs, and examining the possible roles of reference librarians in IRs. Design/methodology/approach - Key IR and open access concepts are clarified and critiqued. New organizational roles for reference libraries are suggested that build on their current functions. Findings - The IR concept is defined, and IRs are shown to be different from scholars' personal web sites, academic department/unit archives, institutional e-print archives, and disciplinary archives. Open access is defined and examined. While the vision of open access is clear, the implementation of the vision is less pure. Open access and IRs are not synonyms: IRs are best seen as an enabling technology for open access. Reference librarians must play a key role in IRs, and ten potential IR support activities for them are identified. Originality/value - This paper orients reference librarians, library administrators, and others to IRs and open access, providing a context for understanding how reference librarians' jobs may be transformed by the emergence of IRs.