First results of a 3-cm (9.7 GHz) and 2-mm (140 GHz) waveband EPR study on the magnetic and electron-transport properties over a wide temperature range are reported for the crystalline phase of polyaniline highly doped with p-toluenesulfonic acid. The nature of charge carriers was analyzed and the mechanism of charge transport was established. The spin–lattice and spin–spin relaxation times were measured using the continuous saturation technique. Quasi-three-dimensional (Q3D) domains with a high conductivity are formed in polyaniline by doping. The effective electric conductivity of the polymer is determined by Mott Q3D hopping in domains of this type and Q1D variable-range hopping between these domains. There is no correlation between charge transport and spin relaxation processes.