The study deals with the examination of the rheological behaviour of rubber blends which were filled with bentonite. The filler - polymer as well as the filler - filler interactions were studied and determined from the frequency sweep and strain sweep rheological measurements. The used natural bentonite was extracted from the locality called Jelsovy Potok. The natural bentonite had a fine fraction with a particle size of 15 µm a 45 µm and it was added into rubber blends as a partial replacement of commonly used filler. The rubber blends were characterised on the basis of curing characteristics (minimum torque M_L, maximum torque M_H, optimum time of cure t_(c90), processing safety of blend t_s). Moreover, the complex viscosity and Payne effect were also specified. The required measurements were done by using PRPA 2000.