ABSTRACTEskers sometimes become much wider and higher for short sections. As a special form element such sections are calledesker enlargementsin this paper. Comparative studies of these relatively uncommon phenomena have been carried out in inland areas of northern Sweden above the highest shoreline of the Baltic.The esker enlargements show some common distinctive features such as dead ice kettles, often a rather flat topped surface with shallow erosion channels and superimposed nets of low eskers (esker ribs) descending diagonally the side of the main esker in the flow direction, and sometimes a broken topography with high mounds. All these features indicate fractured ice during at least a part of their formation, during the last deglaciation period. The continuation of the esker upstream and downstream of the esker enlargement is often a low, narrow and winding ridge, sometimes in a depression, often a lake (esker in the lake).The formation of esker enlargements seems to be caused by changed hydrologic conditions, partly due to the surrounding topography e.g. in the form of a widening, sometimes curving valley. In only one locality out of three seismically investigated ones, is there a connection between the esker enlargement and the underlying bedrock topography, in the form of a rising bedrock surface in the flow direction. However, changed hydrologic conditions can also be caused by previously deposited esker material or till, forcing the water flow to rise with a diminished speed of water flow and transport capacity as a result. Under these conditions the esker enlargements are formed in at least two steps: (1) subglacial deposits of esker or till material, (2) transformation of the upper parts of these deposits by subglacial and subaerial glaciofluvial processes. Apart from the positions of the sites in a rapidly melting land ice with ice-dammed lakes, the large amount of material necessary for the formation of esker enlargements is sometimes due to the confluence of drainage systems shown in the form of connecting eskers.