The Three Rs tenet (Replacement, Reduction and Refinement) guides scientists on the ethical use of animals in science.

• Replacement refers to methods which avoid or replace the use of animals in an area where animals would otherwise have been used
• Reduction refers to any strategy that will result in fewer animals being used
• Refinement refers to the modification of husbandry or experimental procedures to minimize pain and distress

The Three Rs concept originated from the scientific community and is a widely accepted cornerstone of policies on animal-based science around the world. Ethical animal use requires consideration of animal welfare needs.

Many scientific advances in the Three Rs are reported in dedicated journals and on the websites of Three Rs Centres around the world.

In Canada oversight of scientific animal use is the responsibility of the Canadian Council on Animal Care (CCAC) and is described on the CCAC website.