I think animals have as much a right to a happy life as we do and would therefore love to say NO!
BUT... (with my limited knowledge on the subject) as many people have already said, I think that unfortunately testing on animals IS necessary in certain areas.
The world would be a very different place without it. As long as we maintain some form of control over it (ie licences etc) and it is performed with minimum cruelty.
I'd say no to testing on cosmetics etc.... but then again, what if a cosmetic is released that then causes cancer and thousands of people die who wouldn't have done otherwise, when a minimal amount of testing on an animal would have saved them...? really not sure what I think about that....