The 3Rs

Humane animal research should follow the principles of Replacement, Reduction, & Refinement (the 3Rs). These principles were laid out 60 years ago in the book The Principles of Humane Experimental Techniques by William Russell and Rex Birch. The 3Rs are internationally accepted principles for the ethical consideration of animals in research. They are often key goals for organizations and regulatory bodies that conduct animal research. Furthermore, public attitudes towards animal research are more positive when the 3Rs are used. For information about the 3Rs for the public see this webpage.

The NA3RsC is an organization that is committed to advancing the 3Rs. We facilitate communication, sharing, and collaboration to bring transformational solutions to advance science and animal welfare.

Defining the 3Rs & What NA3RsC is Doing

Refinement refers to methods that minimize pain, suffering, and distress of research animals as well as improving their welfare.

  • Refinement can include animal housing and husbandry. For example, providing housing that allows the expression of species-specific behaviors, modifying handling methods, and training animals to cooperate with handling. NA3RsC has an initiative focused on Refinement.

Reduction refers to methods that minimize the numbers of animals required per experiment or study designs to achieve robust results.

  • Reduction also refers to methods that maximize the amount of information gathered per animal in an experiment. For example, NA3RsC has an initiative focused on Translational Digital Biomarkers.
  • Sharing data and resources between research groups can also contribute to reduction so that multiple groups can look at the same data to different ends.

Replacement refers to methods or technologies which avoid, or replace, the use of animals

  • Full replacement refers to replacing living animals with non-animal methods. For example, NA3RsC has an initiative focused on Microphysiological Systems.
  • Partial or relative replacement refers to replacing animals with animals that are not considered capable of experiencing pain/distress such as invertebrates like Drosophila, nematode worms, and social amoebae, and immature forms of vertebrates. Partial replacement also includes using cells or tissues from animals killed solely for this purpose.

For full-length webinars with practical tips about the 3Rs you can watch webinars produced by the National Centre for the 3Rs and real-world scientists hosted on