Palaeoseismological techniques applied with artificial trenches at three deep-seated gravity slope deformations (DSGSDs) in the Alps document extensional deformation and reverse slips. The data indicate that reverse slip might occur both at the toe and in the central-upper portions of DSGSDs. The reverse slip is interpreted as due either to locking of the frontal blocks of a DSGSD or to the relative decrease in the rate of downward movement in the frontal blocks with respect to the rear blocks.