It is now commonly recognized that many geotechnical problems are related to the unsaturated behavior of soils. Such is the case for phenomena occurring at shallow depths in the so-called vadose zone. Unsaturated flow is also very important for the management of milling wastes, especially for seepage in and around tailings ponds. Suction properties constitute a key element for the functional representation of unsaturated flow conditions. These are usually shown by the water retention curve, which gives the relationship between volumetric water content ( theta ) and matric suction ( psi ). Laboratory measurements have been performed on three different tailings from hard-rock mines in the Abitibi region to study the effect of various factors, including grain size and porosity, on the theta - psi relationship. The main results are presented in this paper. The data are first analyzed using a well-known descriptive model. The experimental results are also used to estimate the air-entry value according to various procedures including a simple method proposed by the authors. Then, it is shown how an existing predictive model can be modified to obtain, from basic material properties, the complete water retention curve.Key words: unsaturated flow, tailings, water retention curve, moisture content, saturation ratio, porosity.