With regard to the stability of the slope, the construction of sealing systems for landfills on inclined areas requires an exact knowledge of the short- and long-term behaviour of geosynthetics as well as the interaction of the individual components and the system as a whole. The construction of sealing systems with steep slopes is of great interest for economical reasons. When the inclination of a slope is increased from e.g. 1 : 4 (vertical : horizontal) to 1 : 2.5 the storage capacity is raised by approx. 60 %: The friction behaviour of the contact shear surfaces together with the maximum admissible stress on geosyntn tic layers is vitally important. It is the purpose of reinforcement layers with the lining system to take up and conduct tensile forces both for short- and long-term periods. This paper presents stability calculations which have proven their effectiveness in practice.