Sammendrag
The 18th intercalibration of invertebrates in the ICP Waters programme had contribution from three laboratories. 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 ranged between 96.0 and 97.1, well above the value 80 - indicating very good taxonomic work.