Each year, reports Santa Clara University, approximately 20 million animals are used in medical experiments or to test products, many of them dying in the process. Animal rights advocates argue that such testing is unnecessary and cruel, while proponents of animal testing believe that the benefits to humans outweigh the moral issues.

One argument against animal testing is that there are often more acceptable alternatives. For example, scientists can test whether chemicals will irritate the eyes using the blood vessel-rich membrane lining a hen's egg, rather than exposing the eyes of living animals to the chemical. Cells grown in a test tube (in vitro) and computer simulations can offer a good idea of how animals and humans would respond to certain tests. Those against animal testing advocate three Rs: replacement (finding alternative methods of testing), reduction (using animal testing as little as necessary) and refinement (making sure that animal testing is done in the most humane and pain-free fashion).

Alternatives to animal testing do not always work, however, because the system of a living organism can be unpredictable. If scientists perform tests on computer models, test tube-grown cells or “lower organisms” (such as eggs or invertebrates, rather than warm-blooded animals), they may not see as full a picture of the test results as they would with testing on live animals (or animals which are more similar to humans). In order to fully understand a live organism's system, scientists must perform animal testing at some point.

Animal rights advocates argue that testing on animals is cruel and unnecessary. Some connect animal testing to racism or sexism, arguing that all living creatures are worthy of respect and that making animals suffer for any reason is morally wrong. Dr. Tom Regan, a leader in the animal rights movement, writes that animals “have beliefs and desires; perception, memory, and a sense of the future.” The argument that animal testing may be necessary is no excuse, from this point of view, because it is the responsibility of scientists to discover humane alternatives.

Those in favor of animal testing argue that it has led to many advances in science, increasing the quality of life for both humans and animals. Animal testing has helped us develop vaccines, surgeries, cancer treatments and other life-saving medical advances. Although animal testing may cause pain to a few animals, many believe that the greater good of humanity outweighs this cost.