Guinea pigs accounted for 133,562 of the animals covered under the Animal Welfare Act (AWA) that were held or used in research and teaching in the U.S. in 2024. Guinea pigs were among the first widely used animals in the research laboratory and have been used as an animal model for over 200 years, which is why the term “guinea pig” is associated with scientific experimentation. Guinea pigs were originally used for infectious disease research, including studies of tuberculosis and diphtheria. They continue to be used as models in infectious disease studies. They are also used for a wide range of other topics including safety tests and toxicity studies; allergy research; research involving the respiratory, nervous, and immune systems; nutritional research; and auditory system studies.