Classifying research proposals by risk of harm is fundamental to the approval process and the most pivotal risk category in most regulations is that of “minimal risk.” If studies have no more than a minimal risk, for example, a nearly worldwide consensus exists that review boards may sometimes: (1) expedite review, (2) waive or modify some or all elements of informed consent, or (3) enroll vulnerable subjects including healthy children, incapacitated persons and prisoners even if studies do not hold out (...) direct benefits to them. The moral and social purposes behind this threshold are discussed along with relevant views from the National Commission, NBAC, NHRPAC, Grimes v. Kennedy Krieger Institute, The Nuremberg Code, and The WMA's Declaration of Helsinki. Representative policies from Australia, Canada, South Africa, the U.S., and CIOMS are reviewed revealing different understandings of this sorting threshold. Six of nine frequently cited interpretations of “minimal risk” are untenable. The “absolute” interpretation of the “routine examination” standard is defended as best. (shrink)