The Silver Spring monkeys were 17 wild-born macaque monkeys from the Philippines who were kept in the Institute of Behavioral Research in Silver Spring, Maryland. From 1981 until 1991, they became what one writer called the most famous lab animals in history, as a result of a battle between animal researchers, animal advocates, politicians, and the courts over whether to use them in research or release them to a sanctuary. Within the scientific community, the monkeys became known for their use in experiments into neuroplasticity—the ability of the adult primate brain to reorganize itself—regarded by some as one of the most exciting discoveries of the 20th century. But it came at a large cost.

The monkeys had been used as research subjects by Edward Taub, a psychologist, who had cut afferent ganglia that supplied sensation to the brain from their arms, then used arm slings to restrain either the good or deafferented arm to train them to use the limbs they could not feel. In May 1981, Alex Pacheco of the animal-rights group People for the Ethical Treatment of Animals (PETA) began working undercover in the lab, and alerted police to what PETA viewed as unacceptable living conditions for the monkeys. In what was the first police raid in the U.S. against an animal researcher, police entered the Institute and removed the monkeys, charging Taub with 17 counts of animal cruelty and failing to provide adequate veterinary care. He was convicted on six counts; five were overturned during a second trial, and the final conviction was overturned on appeal in 1983, when the court ruled that Maryland's animal cruelty legislation did not apply to federally funded laboratories.

The ensuing battle over the monkeys' custody saw celebrities and politicians campaign for the monkeys' release, an amendment in 1985 to the Animal Welfare Act, the transformation of PETA from a group of friends into a national movement, the creation of the first North American Animal Liberation Front cell, and the first animal research case to reach the United States Supreme Court. In July 1991, PETA's application to the Supreme Court for custody was rejected, and days later the last of the monkeys were killed.