Customs laboratories are a very important instrument for customs authorities and, in general, for national administrations.

Their traditional work is the chemical analysis to determine tariff classification and the level of duties and other taxes. In the last years, their role has also evolved over time with changes in trade patterns and technical evolution. Therefore, modern customs laboratories now play an important part in environmental protection (e.g., controlling the trade of ozone depleting substances), endangered species protection, control of dangerous goods such as pesticides, persistent organic pollutants, chemical weapon, as well as narcotics and drug precursors, etc.

In order to assist its Members improve or implement an efficient Customs Laboratory, the WCO has developed a practical handbook (The Customs Laboratory Guide - Restricted access) which includes the "best practices" covering a variety of laboratory operations. In addition the WCO has developed a comprehensive technical assistance and training programme.