The main objective of an ongoing project of the German Federal Environmental Agency (UBA) was to assess whether drinking water production by slow sand and bank filtration is endangered by the occurence of microcystins in surface waters and if the elimination potential of the sand or sediment with respect to microcystins is high enough to ensure safe drinking water production throughout the year. For this reason, experiments using technical scale slow sand filters were conducted with microcystins on the UBA's experimental field in Berlin. In addition, field investigations were carried out on a transect of observation wells situated between Berlin's Lake Wannsee and one of the drinking water wells of the water works. Includes 5 references.