Read-across plays an important role in hazard assessment of chemicals under numerous internal and external regulatory programs.It is used in association with the formation of categories or small groups of analogous chemicals, and these are typically developed based on structural similarity and, increasingly often, also on mechanistic (biological) similarity.The global acceptance of read-across is variable.For instance read-across and analogous techiques are widely used as part of the US EPA"s Pre-Manufactory Notification Process.Within the European Union, more understanding of the acceptance of read-across for toxicity prediction in the regulatory contextis required.Notably, the European Union REACH legislation explicitly calls for the use of non-animal alternative methods and thus opens up the use of read-across, and in 2015 the European Chemicals Agency (ECHA) published their Read-Across Assessment Framework (RAAF) as a structured approach to the scientific evaluation of read-across justifications included in REACH registration dossiers.The RAAF details the crucial scientific aspects that should be considered and discussed in the rationale provided to support a SAR-based read-across assessment.A summary of the analysis of the RAAF, the utility of the RAAF in preparing and evaluating the read-across justification and available supporting evidence to minimize the uncertainty will be presented.A list of the key aspects that should be considered in any scientifically robust SAR-based read-across assessment will be discussed.In the end, ideas about how can we overcome the barriers inhibiting application of read-across methodologies in regulatory decision-making today will be also explained.