The 3Rs

The 3Rs refer to the terms Replacement, Reduction and Refinement, principles which were originally defined by William Russell and Rex Burch in 1959. The 3Rs aim to improve the welfare of animals used in science or education, while advancing the quality of scientific and medical testing. The 3R principles remain a fundamental concept in laboratory animal science today, underpinning EU and national legislation on the protection and welfare of animals used for scientific purposes. These principles also apply to the conduct of studies used in domestic animals as well as wild animals or birds that might be the subject of research projects.  

Replacement          Reduction          Refinement

Article 4 of EU Directive 2010/63/EU describes the requirements for the 3Rs. 



Article 4 (1): “Member States shall ensure that, wherever possible, a scientifically satisfactory method or testing strategy, not entailing the use of live animals, shall be used instead of a procedure.”
The HPRA understands this to mean that ‘alternative’ methods are to be used where possible instead of live animals. Examples of alternative methods would include in vitro tests such as cell lines, computer simulation and modelling, video material, or the use of invertebrates such as fruit flies or worms. However, in cases where there is no alternative to the use of live animals, the HPRA’s goal is to ensure that the highest standards of animal welfare and care are applied.



Article 4 (2): “Member States shall ensure that the number of animals used in projects is reduced to a minimum without compromising the objectives of the project.”

A common misconception is that Reduction simply refers to decreasing the total number of animals used for scientific purposes. However, the principle of Reduction is to ensure that the appropriate number of animals are used for each project. This allows scientists to obtain statistically robust data without using more animals than are necessary. The use of more animals than necessary in a project is not in keeping with the principle of Reduction. However, using too few animals in a project is not in keeping with the principle of Reduction either, and can be equally detrimental. If too few animals are used in a project, the results obtained may not be reproducible and therefore are invalid and the animals used for this purpose will have gone to waste. Therefore the HPRA believes that Reduction should start with good experimental design and planning.
In addition, Reduction applies to the sharing of resources and tissues between research groups. The use of new technologies can also reduce the need for additional animals. For example, new imaging techniques can facilitate longitudinal studies in the same animal, rather than having to use multiple animals at various points in time through a study.




Article 4 (3): “Member States shall ensure refinement of breeding, accommodation and care, and of methods used in procedures, eliminating or reducing to the minimum any possible pain, suffering, distress or lasting harm to the animals.”
The HPRA understands Refinement to mean that animals used for science are provided with the best possible care and that suffering is reduced to an absolute minimum whilst undergoing procedures. Refinement techniques would include, for example, careful handling by trained individuals, the provision of high standards of housing and husbandry to include enrichment materials (e.g. toys and nesting material) and the appropriate use of anaesthesia and pain relief during procedures.   


For further information on the 3Rs, see the links below. 


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General 3Rs information:


The NC3Rs (National Centre for the Replacement, Refinement and Reduction of Animals in Research) is the UK’s national organisation which works to discover and apply new technologies and approaches to replace, reduce and refine the use of animals in science. It is an excellent resource for all 3Rs related information.
 The NC3Rs has released a video resource for introductory training on the 3Rs. The video provides definitions of the 3Rs, practical advice on how to implement the 3Rs and video case studies of the 3Rs research. This video will help researchers and aspiring researchers to understand how the principles of the 3Rs can drive better science and improve animal welfare.


The 3R Guide database 

This database is a collaboration between Norecopa, which is Norway’s 3R Centre, and the US Department of Agriculture’s Animal Welfare Information Center. It is a searchable 3Rs database with resources such as guidelines, journals and websites.

The 3Rs Microsite

This is a Canadian website dedicated to the 3Rs which has a 3Rs search guide, as well as other resources for researchers using both farm and laboratory animals. 




EURL ECVAM is the European Union Reference Laboratory for alternatives to animal testing. It is involved in validating and promoting alternative testing methods. The website is a good source of advice on theoretical and practical aspects of test validation, the current state of validation of alternative methods, as well as general animal welfare issues such as the use of genetically altered animals.


FRAME is the Fund for the Replacement of Animals in Medical Experimentation and its ultimate aim is to eliminate the need to use laboratory animals in the future. Until this is possible, FRAME works to support Reduction. The FRAME website has information about good experimental design (including training courses), and current projects which are working to identify non-animal alternative test methods.


TSAR is the Tracking System for Alternative test methods review, validation and approval in the context of EU Regulations on chemicals. The website provides information on the status of alternative methods as they progress from scientific proposals, through development, validation and regulatory approval, to eventually being used in a regulatory context.


NORINA is a Norwegian Inventory of Alternatives, a database containing information on over 3,500 audiovisual aids that may be used as alternatives or supplements to the use of animals in education and training



FRAME is the Fund for the Replacement of Animals in Medical Experimentation and its ultimate aim is to eliminate the need to use laboratory animals in the future. Until this is possible, FRAME works to support Reduction. The FRAME website has information about good experimental design (including training courses), and current projects which are working to find non-animal alternative test methods.  

The Experimental Design Assistant

The Experimental Design Assistant is an NC3Rs online tool to guide researchers through the design of their experiments in order to ensure that they use the minimum number of animals consistent with the scientific objectives, as well as using methods to reduce bias.

ARRIVE Guidelines

The ARRIVE (Animal Research: Reporting of In Vivo Experiments) guidelines by the NC3Rs are a helpful set of guidelines created with the intention of improving the reporting of research using animals. The HPRA encourages the use of the ARRIVE Guidelines when designing animal studies.


USDA Animal Welfare Information Center (AWIC)

This is a US based site, which provides information on improved animal care and use in research, testing, and teaching. 

FLAIR e-learning

This excellent website provides free interactive resources to support the training of laboratory animal research workers and to continue the professional development of others who work with laboratory animals. E-learning modules include assessment of welfare and laboratory animal anaesthesia. 

Humane Endpoints website

This website created by the 3Rs-Centre Utrecht Life Sciences provides useful guidance on how to apply humane endpoints and identify pain and distress in mice and rats. 

Procedures With Care

This is a website which provides a series of resources (such as videos) to support the adoption of best practice for commonly used procedures in animal research.  
PREPARE Guidelines 

Links on Model Refinements

The HPRA strongly encourages scientists to work on refining their animal models. The following papers are recommended reading:




For other useful links please click here.

If you have any queries about these links, or suggestions for additional useful 3Rs resources that could be included here, please email