The application of radar interferometry to detect slope movements on the order of millimeters to centimeters per year is demonstrated. The deformation field of a slope above a hydropower reservoir in the Austrian Alps was derived from SAR interferometric pairs of the satellites ERS‐1 and ERS‐2, acquired between July 1992 and August 1998. Above the treeline it was possible to map the motion from interferograms covering time spans up to three years. Whereas ground‐based geodetic measurements focussed on the movements of the lower slope section, the interferometric analysis shows that the mass wasting processes affect the entire slope of 1000 m vertical extent. Significant interannual differences of the displacement rates became apparent which were found to be related to the pattern of summer rainfall.