Although use of the LD50 Test is still required by law in some countries, many countries now accept other methods. Its purpose is to give a measure of how poisonous or toxic chemicals are.

However, scientists and animal welfare, animal protection and other groups have been active in trying to find alternatives to the LD50 test.

So far three have been found. These are called the Fixed Dose Test, the Up and Down Procedure and the Acute Toxic Class methods.

These approaches substantially reduce the number of animals which are needed to find out how poisonous a chemical is, from 60-80 with the LD50 Test at its worst to 6-10. They also substantially reduce the number of animals showing signs of poisoning and how bad those signs are. These tests are examples of Reduction and Refinement, but not Replacement.