Objectives: To examine differences in the ethical judgments made by Research Ethics Committees (RECs) or Institutional Review Boards (IRBs).

Methods: We did a review of the literature and included any study that attempted to compare the ethical judgments made by different RECs or IRBs when reviewing one or more protocol.

Results: There were twenty-six articles reporting such discrepancies across Europe, within the United Kingdom, Spain, and United States. Of these studies, there were only five reports of some RECs approving while others rejecting the same protocol. All studies, however, reported differences in the clarifications and revisions asked of researchers regarding consent, recruitment, risks and benefits, compensation arrangements, and scientific issues.

Conclusions: The studies were generally anecdotal reports of researchers trying to do research. New rules requiring a single ethical opinion for multi-site research at least in European Member States may simply conceal problematic issues in REC decision making. In the last analysis, we should expect a certain degree of variation and differences if we are to keep a committee system of review, although there is a pressing need to investigate the way in which RECs make these judgments. In particular, we need to identify the source of any aberrations, distortions, or confusions that could arbitrarily affect these judgments. Furthermore, local conditions remain important ethical considerations and should not be sidelined in pursuit of greater “consistency.”