The 17th intercalibration of invertebrates in the ICP Waters programme had contribution from four laboratories. The laboratories identified a very high portion of the individuals in the test samples, usually > 95% of the total number of species. On the genus level, few faults were recorded. The mean Quality assurance index ranged between 96.2 and 99.0, well above the value 80 - indicating excellent taxonomic work. The ICP Waters Intercalibration 2013 gave the best results ever achieved during 17 years of testing.