In recent years the use of chimpanzees for biomedical research and testing has been restricted in many countries. The U.S. is one of the last countries, which decided to retire chimpanzees from research. Sadly, that researches had been the causes of suffering of chimpanzees for many years. These researches were mostly unnecessary and unsuccessful. Researches with chimpanzees started in the U.S in early 1920’s by psychologist Robert M. Yerkes who was interested in learning about nonhuman primates’ behavior.( ) Scientists use these animals because chimpanzees and humans share a common ancestry. Chimpanzee DNA is approximately 96-98 percent identical, and the structure and function of the brain is similar with human brain. As a result, chimpanzees and humans share physiological, emotional, and behavioral traits. In the 1940s, Yerkes National Primate Reserch Center started to use chimpanzees in medical testing. Chimpanzees are the closest genetic relative of humans. They make families and as our parents would care about us, mothers of infants chimps would protect and deeply care about them. They help each other, share cultural traditions and suffer when their lost loved ones. In laboratories chimpanzees live alone in small metal cages for years. Isolated animals becoming aggressive and experience depression and eventually lose their minds. It is important to mantion that even when chimps in labs do not involved in experiments they still experience fear because they can see suffering from pain other primates and expecting being next. In the 1960s, Carleton Gajdusek, an American doctor, injected three chimpanzees with brain tissue from victims who died of kuru. All three chimpanzees were infected with transmissible spongiform encephalopathies (TSEs) which is a neurodegenerative disease caused by an abnormal proteinaceous particle termed a “prion.” Chimpanzees became seriously ill and, their response to the disease was identical