Research participants require ongoing protection of the kind already established in law and regulation. However, "special scrutiny" for certain types of research is also needed. Three criteria for special scrutiny are 1) research that involves initial experiences of translating new scientific advances into humans, especially when the intervention is novel, irreversible, or both; 2) research with a known or credible risk for significant harm (death or serious disability are the clearest examples) to research participants as a consequence of the experimental intervention and with no potential for offsetting direct medical benefit; or 3) research with a protocol that raises ethical questions about research design or implementation for which there is no consensus. Special scrutiny recognizes that not all research protocols are equally ethically challenging and aims to provide appropriate protection for all research participants.