The field of quality assurance is beset by an extensive and sometimes confusing termilogy, the use of which has still t been universally agreed on or accepted by laboratories or interested professional bodies worldwide. This glossary contains some of the most commonly used expressions in these fields, including those which appear in UNODC publications on quality assurance, and is an attempt to help promote and harmonise national efforts by providing internationally acceptable termilogy. It is intended to be an aid to analysts in the implementation of quality assurance programmes and good laboratory practices, and is provided to laboratories as an educational document, and as a means of encouraging laboratories to collaborate and participate in quality assurance matters. As a result, the Glossary includes more than one definition of a word or phrase where these might improve understanding of what they mean. The current publication is an update of the first edition of the Glossary of Quality Assurance Terms. This second edition includes many new terms which have appeared in UNODC publications since the Glossary was first published.