The steady-flow and creep behavior was measured for suspensions flocculated by a soluble polymer. When a polymer chain attaches to the surface at several points, the adsorption is essentially irreversible. The suspensions flocculated by irreversible bridging are shear thinning over a wide range of:shear rates. At low stresses, the deformation of bridges can accumulate elastic energy. As a result, the suspensions show viscoelastic responses with long : relaxation times. The addition of surfactant decreases the fraction of segments adsorbed in trains and increases the reversibility of polymer adsorption. : The bridges are constantly forming and breaking in a quiescent state. Since the polymer coils have the equilibrium conformation, the flow is Newtonian at low shear rates. When the surface is completely covered with surfactant, the nonadsorbing polymer coils give rise to depletion flocculation due to attractive forces generated by exclusion of the free polymer from the interparticle space. The suspensions flocculated by depletion are also shear thinning. However, the particle bonds show little resistance with respect to the transverse bending force. Because of rapid dissipation of energy by the shear motion of particles, the suspensions behave as liquids with very weak elasticity. Thus, the theological properties of suspensions can be controlled by the affinity between the polymer chains and particle surface.