The “Blekkinkveen” is a little holocene marsh near Winterswijk (prov. of Gelderland, Netherlands). It was known by the occurance of marshchalk containing freshwatermolluscs. Several auger-drillings have been made to investigate the extension of the former marsh. Also the molluscan contents of the chalk was studied. The results of the drillings and a list of the molluscan fauna are given.