Intro

The Animals

The Science

The Alternatives

Animal testing can be replaced with better alternatives. These are, among others:

Computer Models
Running data through tests to establish the most likely drugs and toxicity is fast and cheap. It provides the initial stages in testing and can rule out drugs which are toxic to humans.
This should also be used before animal testing, however, many places still test on animals before using computers. This is often attributed to laziness and habit.

Cell Testing
Waste human tissue and cultured cells can be tested on to establish toxicity and likely reactions. Again, this relatively inexpensive method is still not always used before animal testing. Also, entire body parts can replicated. Scientists have grown eye corneas.
Drugs which have passed animal trials have gone on to kill humans. These drugs, when tested on human cells, reproduced the same reaction that killed the humans. Had this method been used before, these people would not have died.

Human Based
Human volunteers can be given safe micro-doses which can then be tracked to discover how the body reacts. Irritants can be safely tested on humans as irritants create reversible, temporary, damage.