Structure-activity relationships and quantitative structure-activity relationships, collectively referred to as (Q)SARs, are simplified mathematical representations of complex chemical-biological interactions that can be used to predict the physicochemical and biological properties of molecules. They can take various forms of various complexity and either be qualitative or quantitative.
A structure-activity relationship (SAR) usually represents an association between a chemical substructure and the potential of a chemical containing the substructure to exhibit a certain biological effect.
A quantitative structure-activity relationship (QSAR) quantitatives relates the properties of a chemical (encoded in its chemical structure) to a physical property or to a biological effect (e.g. a toxicological endpoint).

IHCP, DB-ALM website

(Q)SARs are methods for estimating properties of a chemical from its molecular structure and have the potential to provide information on hazards of chemicals, while reducing time, monetary cost and animal testing currently needed.
To facilitate practical application of (Q)SAR approaches in regulatory contexts by governments and industry and to improve their regulatory acceptance, the OECD (Q)SAR project has developed various outcomes such as the principles for the validation of (Q)SAR models, guidance documents as well as the (Q)SAR Application Toolbox. The OECD (Q)SAR Project is carried out with the financial assistance of the EU.
Source: OECD


Animal tests can be avoided if the hazardous properties of a substance can be predicted using computer models. The [(Q)SAR] [(quantitative) structure-activity relationship] approach seeks to predict the intrinsic properties of chemicals by using various databases and theoretical models, instead of conducting tests. Based on knowledge of chemical structure, QSAR quantitatively relates characteristics of the chemical to a measure of a particular activity. QSAR should be distinguished from SAR, which makes qualitative conclusions about the presence or absence of a property of a substance, based on a structural feature of the substance. 

Source: ECHA
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  • (Q)SARs
  • (Q)SAR
  • QSAR
  • (Quantitative) Structure-Activity Relationships
  • structure–activity relationships