The Three Rs (3Rs) are guiding principles for more ethical use of animals in product testing and scientific research. They were first described by W. M. S. Russell and in 1959. The 3Rs are: 1. * Replacement: methods which avoid or replace the use of animals in research 2. * Reduction: use of methods that enable researchers to obtain comparable levels of information from fewer animals, or to obtain more information from the same number of animals. 3. * Refinement: use of methods that alleviate or minimize potential pain, suffering or distress, and enhance animal welfare for the animals used.