Why do scientists use animals in research?
A doctor gives a student a shot.

Scientists use animals to learn more about health problems that affect both humans and animals, and to assure the safety of new medical treatments.

Medical researchers need to understand health problems before they can develop ways to treat them. Some diseases and health problems involve processes that can only be studied in a living organism. Animals are necessary to medical research when it is impractical or unethical to use humans.

Animals make good research subjects for a variety of reasons. Animals are biologically similar to humans. They are susceptible to many of the same health problems, and they have short life-cycles so they can easily be studied throughout their whole life-span or across several generations. In addition, scientists can easily control the environment around the animal (diet, temperature, lighting, etc.), which would be difficult to do with people. However, the most important reason why animals are used is that it would be wrong to deliberately expose human beings to health risks in order to observe the course of a disease.

Animals are used in research to develop drugs and medical procedures to treat diseases. Scientists may discover such drugs and procedures using alternative research methods that do not involve animals. If the new therapy seems promising, it is tested in animals to see whether it seems to be safe and effective. If the results of the animal studies are good, then human volunteers are asked to take part in a clinical trial. The animal studies are done first to give medical researchers a better idea of what benefits and complications they are likely to see in humans.



Heart Disease

Heart disease and related conditions affect 52 million Americans and cost our nation $274 billion a year. These conditions are the number one killers of men, women, and children. Death rates are declining because of advances in diagnosis, treatment and prevention made through animal research.

The basic mechanisms of heart disease have been studied in dogs, rats, rabbits, cats, sheep, and pigs. Studies with dogs contributed to our most basic understanding of how to manage heart disease. Techniques to diagnose the workings of the heart—electrocardiography, cardiac catheters, angiograms, and coronary blood flow measurement—were developed through research using dogs, as were surgical techniques such as cardiac bypass, angioplasty, and heart transplants.


HIV/AIDS currently affects nearly 1 million Americans. There are treatments but still no cure for this disease that cripples the immune system and is fatal in all but a handful of cases.

Our understanding of the retrovirus that causes HIV/AIDS comes in part from studies of similar viruses in chickens, cats, and monkeys. Promising drugs and possible vaccines are tested first in mice and monkeys before being used in clinical trials with human volunteers.


Treatment of 100 kinds of cancer costs our nation an estimated $107 billion a year. When cancer strikes, cells multiply uncontrollably, gradually overwhelming the body. In the 1930s, less than one cancer victim in five survived for five years. Today, almost half the people diagnosed with cancer will live at least five years, and some never have a recurrence of their disease. There are 8 million Americans alive today who have had cancer.

The chicken provided one of the earliest models of how cancer grows and spreads. An understanding of how viruses cause tumors and the use of hormone treatments to limit tumor growth were developed using rats, mice, rabbits, chickens, monkeys, and horses. Cancer treatments such as chemotherapy drugs, radiation therapy, and various surgical techniques were developed using rodents, dogs, and monkeys, among others.

Bacterial Infections

Bacterial infections are extremely common and affect most people many times during their lives. Although once deadly or disabling, today most are readily treatable with antibiotics.

The effectiveness of penicillin and other antibiotics as treatments for bacterial infections was established through research using mice and other rodents. Scientists continue to use animals to determine what antibiotics are effective against specific organisms, their toxicity, and their potential side effects.

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