There exists an important class of materials, e.g., debris, volcanic lava, sludges, and remoulded sensitive clays, that are known to behave like a Bingham fluid. One of the important properties of a Bingham fluid is the so-called yield stress, and it is usually determined using a coaxial viscometer apparatus. It would be impractical and cumbersome to use this apparatus for many of the materials referred to earlier, and we propose here to examine the use of the slump test. The slump test is used in the concrete industry to evaluate workability and consistency. A statical model is developed to explain the deformation mechanism, and it permits the determination of yield stress. The validity of the statical model is verified using published data on mortar and our own data on Devon silt. The yield stress obtained with the slump test is also compared with the undrained shear strength obtained using the fall cone test. Good agreement is found between the two values. Key words: Bingham fluid, yield stress, slump test, Devon silt.