The mud suspensions under consideration belong to the category of concentrated suspensions which are systems generally exhibiting most of the more complex rheological properties such as thixotropy and yield stress. Because concentrated suspensions can contain coarse particles and exhibit particular rheological properties, a number of experimental difficulties may be encountered with those materials during shear rheometry. The experimental problems considered take the form of disturbing phenomena which typically occur with concentrated suspensions and affect the expected strain field or material homogeneity thus leading to erroneous interpretation of data in terms of the constitutive equation. The consequence of evaporation of the suspending fluid is that the mean solid concentration of the sample increases. For concentrated suspensions there often exists a shear stress threshold which limits a sharp transition in behaviour during creep tests. Suspended particles may migrate through the suspension during flow.