Boreal foraminifers and calcareous nannofossils from the Cenomanian- Turonian boundary interval of the Bohemian Basin were studied. Detailed analyses of foraminiferal assemblages (benthonic diversity, diversity of species, ratio plankton/benthos) showed the important changes within this interval. The benthonic species are dominant within the foraminiferal assemblages, hence the representatives of genus Gavelinella were used for the biozonation. Effects of stressed life conditions on foraminiferal assemblages were recognized within this dysaerobic boundary interval. Similar effects are observed for calcareous nannofossils in the basal Turonian sediments.