A study has been made of asperity interaction of unlubricated steel/rubber sliding pair. The aim is to study the effect of the internal friction (hysteresis) of rubber on the friction force. In the two-dimensional finite element analysis, asperities are modeled by cylinders and both the interfacial adhesion and the friction at steel-rubber interface are neglected. Rate-dependent material behavior of rubber is described, as a first approximation, by a three-parameter Zener-model. It is found that the viscoelastic properties of rubber have a strong influence on the hysteresis component of friction. Distribution of energy loss generated over a cycle of contact in the rubber asperity is also studied. It is concluded that the energy dissipation is most intensive at a certain depth below the rubber surface.