The Adverse Outcome Pathway (AOP) framework has been developed to facilitate the collection of mechanistic information derived from toxicological science in a structured manner, to assist in establishing causal relationships between molecular and cellular events that lead from stressor perturbation of the biology to adverse effects, and to identify critical data gaps in the understanding of those pathways. The objective of the present document is to provide guidance on the quality standards required for the scientific review of an AOP on the AOP-Wiki. It defines the core principles associated with AOP scientific review in order to enable consistent scientific reviews to be conducted, regardless of who is doing the review, and thus will facilitate OECD endorsement.