Electrical conductivity of electrically conductive adhesives is controlled with three mechanisms. These mechanisms are described — a phonon-electron interaction, a constriction mechanism and a tunnel mechanism. If the phonon-electron and constriction mechanisms dominate; the temperature dependence of resistivity is positive and linear, and the temperature coefficient of resistivity is positive. If the tunnel mechanism dominates; the temperature dependence of resistivity is nonlinear and negative and the temperature coefficient of resistivity is negative. Mechanisms of phonon-electron interaction and tunnel dominate in electrically conductive adhesives with isotropic electrical conductivity filled with silver flakes. Measurement of three formulations of adhesives of an epoxy type showed that the tunnel mechanism influences the total electrical resistivity of adhesives significantly.