Animals Used in Research

Facts and Figures

Globally, an estimated 192.1 million animals are used annually for scientific purposes. In the U.S., some of these animals, such as dogs, cats, and primates, are protected under the Animal Welfare Act (AWA), which requires minimum standards of care and mandates reporting on their use. However, the vast majority of animals used in science — approximately 95 to 99% — are not protected by the AWA. Most of these unprotected animals are mice and rats, for which there are no official records. One estimate places the annual number of rats and mice used in U.S. medical research at approximately 111.5 million.

Among animals covered by the AWA, the most recent available data (2019) shows that Massachusetts-based facilities report the highest usage in the country, with around 85,000 animals.

In the context of product testing, the top ten countries in terms of animal use include China (20.5 million), the United States (15.6 million), and Japan (15.0 million), followed by Canada, Australia, South Korea, the United Kingdom, Brazil, Germany, and France. The U.S. ranks second globally in the number of dogs used for testing.

Brief History

The practice of using live animals in science dates back to ancient Greece and Rome, when vivisection, the cutting of live animals to study internal functions, was performed without anesthesia. While some early objections arose during the Renaissance and Enlightenment, the first organized protest against vivisection occurred in 1863, led by British women in Florence. The United Kingdom soon passed the Cruelty to Animals Act in 1876, requiring anesthetics during vivisection.

At the same time, scientific texts such as Darwin’s On the Origin of Species (1859) and Bernard’s An Introduction to the Study of Experimental Medicine (1865) helped popularize animal research as a scientific method. The practice expanded significantly after World War II with the influx of federal funding in the U.S.

Congress first attempted to regulate laboratory animal care with the 1966 Laboratory Animal Welfare Act, which later became the Animal Welfare Act. Although strengthened over time, the AWA still excludes rats, mice, and birds, leaving the vast majority of lab animals unprotected.

The number of animals used in U.S. research peaked in the 1980s, but public pressure during this time also led many cosmetics companies to replace animal testing with alternative methods. While usage briefly declined in the 1990s, the rise of genetically engineered animals, especially mice and rats, has again increased the overall number of animals used in research.

For What Purpose are Animals Used in Science

Animals are used in laboratories primarily for three purposes:

1. Biomedical Research
   The majority of animals in labs — more than 111 million mice and rats in the U.S. alone — are used in biomedical research to explore disease mechanisms, test treatments, or study human physiology. Supporters argue that animal models have contributed to medical advances such as the development of insulin, antibiotics, chemotherapy, and surgical techniques. However, critics, including many scientists, challenge the validity of animal models due to significant biological differences between species. Notably, over 95% of drugs that pass animal testing fail in human trials, often due to unanticipated side effects or lack of efficacy. Animal testing may also lead to the rejection of potentially beneficial treatments; for instance, penicillin is toxic to guinea pigs but lifesaving in humans.
2. Product Safety Testing
   Federal agencies often require safety testing of items such as cosmetics, household products, and food packaging. These tests may assess toxicity to eyes and skin, potential harm to organs, and effects during pregnancy. Although agencies sometimes allow flexibility in testing methods, traditional animal-based tests remain widely used. Progress has been made in reducing animal use, especially for cosmetics. Companies increasingly share ingredient safety data and use databases and computer models to avoid duplicate testing. Still, most animals used for product testing — an estimated 95% — are not protected under the AWA.
3. Education
   Animal use in education ranges from high school dissection labs to surgical training in veterinary and medical schools. While all U.S. medical schools have phased out the use of live animals, some veterinary schools still use healthy, anesthetized animals for terminal surgical procedures. Many now rely on spay/neuter programs, synthetic models, or donations through Educational Memorial Programs (EMPs), where pet owners donate deceased animals for training purposes. One such model, developed by SynDaver, replicates canine anatomy and functions and may significantly reduce future animal use in veterinary education. In primary and secondary education, millions of animals — including frogs, cats, and fetal pigs — are used in dissection each year, despite the availability of high-quality alternatives such as virtual tools and non-animal models. Seventeen states, along with Washington D.C., protect students’ right to opt out of dissection.

Where Laboratory Animals Come From

Most lab animals are bred specifically for research (purpose-bred), with breeders licensed and regulated by the USDA as Class A dealers. A small number come from “random sources” such as pounds, auctions, or private individuals, and are provided by USDA-licensed Class B dealers. Notably, Massachusetts was the first state to ban “pound seizure,” the practice of transferring animals from shelters to laboratories. Other states have followed, though some still allow it.

Due to public concern, the National Institutes of Health (NIH) reviewed the use of random-source animals in 2009 and, among other conclusions, reported that there were not “any unique or irreplaceable features that made it necessary to obtain random source animals from Class B dealers.” As a result, NIH ended funding for research using random-source cats in 2012 and for dogs in 2014. Today, only a few Class B dealers remain, though their practices continue to raise concern. The HBO documentary Dealing Dogs exposed extreme abuse at one of these facilities, leading to license revocations and fines.

Oversight

The Animal Welfare Act governs the care of all warm-blooded animals used in research — except for rats, mice, and birds — and sets minimum standards for housing, veterinary care, food and water, and environmental conditions. Additionally, the Health Research Extension Act of 1985 provides additional protections for all vertebrates used in research funded by the Public Health Service (PHS), including rats and mice. Institutions receiving PHS funds must follow the Guide for the Care and Use of Laboratory Animals, which outlines standards for humane treatment and housing.

Each research facility must also form an Institutional Animal Care and Use Committee (IACUC), which includes scientists, veterinarians, and at least one unaffiliated member of the public. The IACUC must review and approve all research protocols, inspect facilities, and ensure that alternatives to animal use are considered and that pain is minimized.

The USDA collects annual data from registered research facilities on their use of AWA-covered animals. In 2019 (the most recently available data) of the 934,771 animals reported nationwide: 15% were held but not used in research; 56% were used without pain or distress; 24% experienced pain but received pain relief; and 5% experienced pain and did not receive relief.

After research ends, many animals are euthanized, though some die during procedures or are kept in poor conditions until they are needed. In one prominent case, more than 4,000 beagles were rescued from a breeding facility in Virginia in 2022 and the company was shut down. The MSPCA assisted in the situation and also in the same year passed the “Beagle Bill,” requiring all dogs and cats to be adopted out after their time in research is done.

Expanding the Use of Alternatives

Steps toward ending the use of animals in research generally fall under the framework of the Three Rs: Replacement, Reduction, and Refinement.

• Replacement involves using non-animal systems such as in vitro cell cultures, synthetic organs, or computer models.
• Reduction means minimizing the number of animals needed to obtain meaningful data through improved study design.
• Refinement aims to reduce pain and distress and enhance animal welfare through better housing, handling, and care.

Encouragingly, an increasing number of validated alternatives are helping to reduce animal use and improve conditions for those still in laboratories, and in 2025, the NIH announced that all grant applicants must now consider non-animal methods. According to the agency itself, this shift toward human-relevant science will not only improve medical outcomes but also reduce animal use and suffering.

What Can You Do?

• Stay informed. Public pressure has been the main force behind the improvements that have been made over the years in the laws and regulations protecting animals in laboratories. Join groups that promote laboratory animal welfare, such as the MSPCA, Rise for Animals, the Physicians Committee for Responsible Medicine, and the American Anti-Vivisection Society. These organizations send e-newsletters and alerts to educate members about lab animal issues and let them know when their voice can help laboratory and other animals.
• Be an educated consumer. Consider purchasing products made by companies that are doing the most to develop and promote alternatives to animals in testing their products’ safety. When making investments, consider those companies that don’t test on animals, don’t support animal-based research, or have committed to minimizing the number of animals used to test their products.
• Please see our information on Cruelty-Free Labeling and Product Safety Testing on our website.
• Learn more about pending legislation that could impact animals used in product testing and also a bill that would ban the sale of most cosmetics newly tested on animals.