The third Bi-ennial Global Interlaboratory Assessment on Persistent Organic Pollutants (POPs) was organized in 2016. After invitation to participate in this third round of the proficiency test, 175 laboratories from 66 countries had registered. The test materials included test solutions of analytical standards, the abiotic matrices sediment, air (extract) and water and the biotic matrices fish, human milk and human plasma. The results for the 23 groups of POPs that were listed in the annexes of the Stockholm Convention until 2013 and in addition hexachlorobutadiene were assessed. These resulted in a report with a wealth of information on POP analysis and huge datasets from which the laboratories can evaluate their own methods and performance.