This second Biennial Global Interlaboratory Assessment on Persistent Organic Pollutants was organized in 2012/2013 and was implemented with funds from the European Union through ENRTP and the Global Environment Facility. The degree of participation (105 laboratories from 48 countries) showed the high interest of laboratories to participate in this assessment. All test materials were prepared and distributed. New POPs (polybrominated diphenyl ethers (PBDE), polybrominated biphenyls (PBB), chlordecone (kepone), endosufan, hexachlorocyclohexanes (HCHs) and several perfluorinated alkyl substances (PFASs) were added to the scheme of the initial twelve groups of POPs. The listing of perfluorooctane sulfonic acid (PFOS) and precursors in annex B of the Stockholm Convention necessitated that water was added to the test samples, in addition, an air extract and a transformer oil. High interest for capacity-building resulted in a wealth of information on POP analysis and an enormous data set for this report from which the laboratories can evaluate their methods. Suggestions are given for improvement of methods.