Dispersions of rigid particles in liquids, also referred to as suspensions, form a large group of materials of industrial importance. Both aqueous and nonaqueous dispersions are encountered in industrial applications. This chapter discusses the rheology of dispersions of the three different types of spherical rigid particles: solid spherical particles, porous spherical particles, and electrically charged solid spherical particles. The rheology of dispersions of porous particles is of interest from both practical and fundamental points of view. Dispersions of electrically charged particles are generally more viscous compared to similar dispersions of uncharged particles. When the fluid surrounding the charged particle is set in motion, the electrostatic attraction between the particle’s surface charge and the surrounding charge cloud of counterions hinders the fluid flow inside the double layer and generates additional stresses.