For many centuries people have experimented on animals. There are two main reasons for doing this: first, to find out more about the animals themselves, and, secondly, to test substances and procedures to see if they are harmful. In the second category fall cosmetic products as well as medicines and surgical techniques. There is a growing consensus that it is not acceptable to test cosmetic products on animals. This debate is about whether we should experiment on animals for scientific and medical purposes. The debate about the pros and cons of animal experimentation is one that elicits very strong emotions: animal rights activists have resorted to trespass, violence, death threats, and hunger strikes in their single-minded mission to end this practice.Experiments on animals should be considered on a case-by-case basis. The proper principle to apply, however, is that the reduction of human suffering is our first priority and the prevention of animal suffering or death is secondary to that.