ABSTRACTThe Holocene shorelines of the Mälar valley were according to G. De Geer formed by strong gales during occasional high water levels. They were then uplifted and preserved due to land uplift. Another hypothesis is that the shorelines were formed during eustatic transgressions when the rise of sealevel, at least to some extent, compensated for the isostatic land uplift. In such case several different storm surges would be responsible for the development of a particular shoreline. In order to find out which of the ideas is the more correct one, a study of shorelines in two areas with different land uplift could be of great value. For this study, two regions about 700 km apart, were selected. Some levels of shore-marks are possible to trace at the two areas of investigation. This gives some support to the idea that the shorelines, or rather levels of shoremarks, were formed during times of eustatic transgressions.