The Polar Front along the southeast Greenland Margin denotes the contrasting hydrographic properties of the polar and Atlantic water masses on either side. The remains of planktonic organisms in underlying sediments are expected to reflect these contrasts. To test this, we quantitatively analysed the organic-walled dinoflagellate cyst (dinocyst) assemblages in surface sediments from transects across the present-day Polar Front on the southeast Greenland Margin. Proportional differences are found between the composition of the dinocyst assemblages on either side of the Polar Front. The influence of polar water can be traced in the dinocyst record as high abundances of Algidasphaeridium? minutum and the presence of Pentapharsodinium dalei. The influence of Atlantic water is reflected in the presence of Operculodinium centrocarpum and Selenopemphix quanta. All samples include taxa from both environments, but the quantitative composition of the cyst assemblages clearly reflects the hydrographic features of the overlying surface water masses. Copyright © 2001 John Wiley & Sons, Ltd.