How to use and report (Q)SARs : practical guide; August 2025

REACH foresees in Annex XI that the standard testing regime can be adapted by the use of non-test methods, such as (quantitative) structure-activity relationships [(Q)SARs], if certain conditions are fulfilled. This practical guide extends the chapter on (Q)SARs available in the practical guide on "How to use alternatives to animal testing to fulfil your information requirements for REACH registration". It provides an overview of important aspects to consider when predicting properties of substances using (Q)SAR models as defined in the REACH Regulation - aspects which ECHA also takes into account to evaluate (Q)SAR results. This practical guide also gives useful examples for good prediction practices based on widely used and freely available (Q)SAR software programs. Section 2 of this document gives general information about (Q)SARs and how to use them. Section 3 explains the conditions that need to be fulfilled to use (Q)SAR predictions under REACH. Registrants are advised to explicitly include these considerations in their registration dossiers. Section 4 gives practical examples based on freely available and commonly used (Q)SAR programs. Appendix 1 gives examples (a non-exhaustive list) of (Q)SAR programs available for each of the REACH required endpoints. Appendix 2 provides links to other guidance documents and tools that give further insights into the use of QSARs.