facilitate prioritization of any further test- ing in vivo, for example, as for substances identified as potentially hazardous under the European regulation on Registration, Evaluation, Authorisation, and Restriction of Chemical Substances (REACH) (European Commission 2006). Data generated by the current DNT test method will be vital in the validation of these high-throughput in vitro methods, providing information on their utility and limits, as well as guidance on the potential use of data from these alternative methods in a risk assessment context. Conclusions The OECD DNT TG 426 (OECD 2007) rep- resents the best available science for assessing the potential for DNT in human health risk assessment, and data generated by DNT stud- ies are relevant and reliable for this assessment. The test methods used in the DNT have been subjected to an extensive history of interna- tional validation, peer review, and evaluation that is contained in the public record. The reproducibility, reliability, and sensitivity of these methods have been demonstrated, using a wide variety of test substances. Multiple, independent, expert scientific peer reviews affirm these conclusions, as described in this document. The OECD DNT TG 426 pro- vides an outline of behavioral domains and morphologic end points, relevant to human neurodevelopment, that should be examined to assess potential DNT of a test compound. The results from DNT studies are used for hazard/risk assessment purposes, and in cases where data from a DNT study are not avail- able, additional uncertainty factors may be employed by regulators to address the need for DNT data from a regulatory standpoint. This document shows that a variety of chemi- cals have been tested for DNT, constituting a sampled spectrum of the chemical universe that the test is proposed to investigate. 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