A displaced linear slope (DLS) appears under particular conditions in the current-voltage characteristic of large Josephson tunnel junctions. The significant features that enable one to distinguish the DLS from other structures in theI–V characteristic are discussed. The experimental magnetic field behavior and the temperature dependence of the DLS in different geometrical configurations (cross, in-line, and overlap) are reported; a very consistent behavior has been found for all geometries. Different dynamical states of the junction as a function of both the external magnetic field and the bias current are analyzed. Possible explanations of the DLS in terms of the motion of flux quanta inside the junction are discussed.