ABSTRACT: In recent years, tensions between IRBs and principal investigators (PIs) have risen, posing the needs to understand these conflicts, their underlying causes, and possible solutions. Researchers frequently complain about IRBs, but how IRBs perceive and respond to these criticisms is unclear.I conducted in-depth, semi-structured interviews of two hours each with 46 chairs, administrators, and members. I contacted the leadership of 60 IRBs around the country (every fourth one in the list of the top 240 institutions by NIH funding) and interviewed IRB leaders from 34 of these institutions (response rate = 55%).Interviewees suggest that IRBs and PIs may view the nature and causes of these conflicts very differently and misunderstand each other, exacerbating tensions. Interviewees often recognized that they were seen by PIs as having power, but many IRBs saw themselves as not having it (e.g., because they are "merely following the regulations," and their process is "open," impersonal and unbiased, and they are themselves subject to higher administrative agencies), or as having it, but feeling it is small, and/or justified (e.g., because it is based on overriding goals and "the community values," and IRBs are trying to help PIs). Questions emerge as to whether IRBs do or should have power, and if so, what kind, how much, and when. Several factors may affect these tensions.This study, the first to explore how IRBs perceive and understand conflicts and power relationships with PIs, suggests how IRBs and PIs may differ in viewing their respective roles and relationships, exacerbating tensions. These issues have critical implications for IRBs and PIs--to enhance their awareness and understanding of these conflicts (e.g., that IRBs may have discretionary power) and the underlying causes involved, and for increasing attention to research, practice, and policy concerning these areas of IRB functioning and interactions with PIs.