Six European laboratories participated in the 19th ICP Waters biological intercalibration, which took place in 2015. The laboratories identified a very high portion of the individuals in the test samples, > 95% of the total number of species. On the genus level, few faults were recorded. The mean Quality assurance index was excellent, ranging between 95.4 and 98.5, well above the value 80 - indicating acceptable taxonomic work.