Many today are upset by the use of animals in research. Picture a cute little bunny (they run free around my campus all the time!) or a little mouse; you most likely don't want anything bad to happen to it. Then picture a child receiving life-saving treatment--which would not have been possible without animal research. This just highlights the complexity of the issue.
Guidelines for the use of animals in research
Most people, including researchers, are not psychopaths and sadists trying to cause suffering to any type of being. Today, most animal research is very tightly regulated to cause the least amount of pain and suffering possible to the animal. Additionally, animal research is only approved in experiments where it is considered necessary. In reality, most experiments use cultured cells, yeast, and bacteria whenever possible. Using animals for experimental purposes is very costly because the animals must be pathogen-free (i.e. they can't have any bacterial or viral infection), and they have to be maintained in a controlled environment (i.e. diet, temperature, lighting, etc.). Thus, researchers don't just go outside & set traps for the wild bunnies or mice around campus; instead, labs purchase animals specifically bred for research. The tight regulation of animal experimentation at all research institutions will help prevent any possible abuses.
Animal use in drug research
Although I hate to see animals suffer, I believe animals have helped biomedical research tremendously, and without them we would not have a fraction of the treatments available today. Think about it: do you want to see a new drug tested on your parent, spouse, or child? Do you think it's safer for your loved one to test drugs on animals first? Would you still give your loved one a drug if you knew it killed lab rats? Although drug testing in animals is not perfect (we do have much in common with animals, but there are very important differences), it is one way to screen treatments to make sure none are so obviously unsafe. Additionally, testing in animals often allows researchers to help understand how a drug may work, and this is very important, especially in predicting side effects and potential drug interactions.
Animal use in basic research
Animals are used for more than just testing new drugs. In order to have the best drug possible, a complete understanding of how the body works needs to exist, and this is done through basic research. Do you know how the nervous system works? Much of what we know today about nerves is based upon research of the giant squid axon. Without that research, we would be pretty clueless. Many cancer labs are not testing drugs, but rather they are trying to understand how cancer begins, while others are looking at how it grows and spreads to eventually help such efforts. Think of this type of research as cancer mechanics, and often mice are used to find out how this or that gene may be involved with cancer. How could this type of research be done on humans? Some research is done on human cell cultures and donated tissues, but sometimes looking at cells or tissues reveal little about the effects on the whole body. Animals provide the only means to answer some of these questions, and this type of research is absolutely impossible in humans. Notwithstanding the serious ethics of research on humans, even if it were allowed humans don't have a fast enough generation time (i.e. we can't reproduce until at least 10-14 years of age at the bare minimum). Thus, a researcher could not found out what most genes did in his or her own lifetime. The use of animals in basic research allows discovery to move along rapidly in comparison.
For those who continue to oppose the use of animals in research
You can't talk about animal rights if you have ever benefited from vaccination or the use of any drug (every drug I know of gets tested on animals before going to clinical trials). If you ever are diagnosed with cancer or other life threatening disease, make sure that you receive no treatment that has been tested on animals. (This means you will receive no treatment other than herbal remedies and vitamins--some of which can actually worsen your condition.)
Hear more on the pros of animal research
Americans for Medical Progress Educational Foundation
The New Scientist Editorial--Neglected Benefits of Animal Research
Hear the other side
The Nature of Wellness
Scientific American Editorial--Animal Research Is
Wasteful and Misleading