The Flemish Environment Agency (VMM) is performing biological water quality assessments on inland waters in Flanders (Belgium) since 1989 and sediment quality assessments since 2000. The water quality monitoring network is a combined physico-chemical and biological network, the biological component focusing on macro-invertebrates. The sediment monitoring program produces biological data to assess sediment quality. Both monitoring programs aim to provide index values, applying a similar conceptual methodology based on the presence of macro-invertebrates. The biological data obtained from both monitoring networks are consolidated in the VMM database. The dataset published contains: 283,141 records of 207 observed taxa from 4,152 monitoring sites located on more than 669 different water courses. The data are distributed to the public domain under the Creative Commons CC-BY license. The data in this sampling event resource have been published as a Darwin Core Archive (DwC-A), which is a standardized format for ...