Because they share 99 percent of humans' genetic makeup, chimpanzees have long been used to test medicines being researched for human use. Today, all countries except the U.S. and Gabon have outlawed testing on chimps, and American researchers and animal rights activists remain sharply divided over whether chimp testing should still be allowed.

Chimp Haven, a place for chimps to go after they have been used for animal testing, finds that many of its chimpanzee residents are traumatized and not used to their natural habitats at first. Although some researchers say the chimpanzees are necessary for accurate testing of medicine, others say there are other ways to do the research that aren't as harmful to chimpanzees.

Chimpanzees are especially valuable to researchers who experiment with cures for the disease Hepatitis, since only chimps can contract the same strain as humans. Scientists are working on breeding "human mice" that also respond to Hepatitis the way chimps and humans do, but that research is at least five years from being completed.

"I genuinely care and love these animals. I think a lot of us wouldn't be here, the majority of us would never be here, those who work with animals wouldn't be here if they suffered." - Sabrina Bourgeois, Texas Biomedical Research Institute

"Yes, they are suffering. And then the other thing about it is, the biopsies are not benign. I mean, the chimps that were retired out of this one lab in New York, they died at 35. They can live to be 55, 60 years of age." - Andrew Rowan, Humane Society

1. What kinds of animals are used for medical testing?

2. Why do humans do medical testing on animals?

3. What do you know about chimpanzees and their relationship to humans?

1. Do you think the U.S. should continue medical testing on chimpanzees? Why or why not?

2. Why do you think some chimpanzees who arrived at Chimp Haven were confused by the environment when they first got there?

3. Why are chimpanzees so ideal for medical testing? What's the difference between using chimpanzees and using mice?