The most commonly used animals in laboratories are mice, fish, rats, and birds, but dogs, cats, rabbits, nonhuman primates, and other mammals are also used. In fact, it’s legal to use any type of animal in experiments, although the use of species protected under the U.S. Endangered Species Act may be restricted (for example, chimpanzees). It’s estimated that 10 million to as many as 100 million animals are used in research and testing. But no one knows for certain, because the most frequently used animals, who make up over 93% of all animals in labs, are not protected under the Animal Welfare Act (AWA), and therefore, their numbers are not required to be reported to the U.S. Department of Agriculture (USDA), which enforces the AWA. Unlike the U.S., the European Union provides regulatory and legal protection for these animals, including detailed reporting.

Nearly 775,000 AWA-covered animals were used in USDA regulated facilities in 2023,  according to AAVS analysis of the most recent data released by the agency. For more information about the numbers of AWA animals used in laboratories, including pain categories, visit the USDA’s website.