In the northern part of Sweden there are several natural silt slopes adjacent to local roads or highways. These slopes may have a height of 40?-?50 m and an average inclination close to the friction angle of the material (Fig. 1). One reason that these slopes relatively seldom fail is related to negative porewater pressures (suctions). As knowledge on the size and seasonal variations of negative porewater pressures is limited in Sweden, as well as internationally, conservative values of these pressures have been used in stability calculations. To enhance our knowledge of porewater pressure distribution and its seasonal variations, an investigation was carried out in two selected slopes with the main focus on long-term monitoring of negative porewater pressures (suctions) in slopes related to their stability. The overall aims of the project were to increase the knowledge of seasonal variations of negative porewater pressures, to develop an improved method for field and laboratory testing of silt, and to form the basis for more reliable stability calculations.