The rheological properties of suspensions of ionic and nonionic styrene‐divinyl‐benzene copolymer particles in polycrylamide aqueous solution have been measured by means of a cone‐and‐plate‐type rheometer. The dynamic viscoelasticity of suspensions of nonionic particles is remarkably nonlinear, and frequency‐dependent curves ofG′andG″show the so‐called second plateau. Moreover, the yield stress is characteristic of steady‐flow properties of these suspensions. Suspensions of ionic particles, on the other hand, behave like Newtonian liquids, and the second plateau and yield stress disappear.G′andG″of suspensions of slightly ionized particles do not depend on strain amplitude, while those of suspensions of highly ionized do. Similar measurements have been carried out on suspensions of mixtures of anionic and cationic particles. A suspension containing almost the same number cationic and anionic particles behaves like suspensions of nonionic particles and manifests the second plateau, yield stress, and nonlinear viscoelasticity. An attempt has been made to relate the rheological properties to the aggregate structure, applying the electrical theory for stability of lyophobic colloids.