This volume provides a brief but important summary of the essential tests that need to be performed on all new compounds, whether they be new drugs, pesticides or food additives, before they can be registered for use in the United Kingdom. These basic tests for mutagenicity were originally drawn up by the United Kingdom Environmental Mutagen Society (UKEMS) in 1983. They have now been fully revised by expert working groups from academia and industry under the auspices of UKEMS.