A shift of the Plasmon absorption spectrum into the long-wave region, which increases with decreasing temperature and increasing duration of low-temperature treatment (LTT), was revealed after LTT at 217-77 K of Au hydrosol with a particle size of 10-11 nm. It was demonstrated that a decrease in the effective concentration of conduction electrons (Ne) after LTT is accompanied by an alteration in the damping coefficient of plasma resonance oscillations (y) and the volume fraction of Au particles (Nv). The temperature dependences of y and Nv, just as for silver sol, are stipulated by the tunnel mechanism of the formation of low- temperature defects in the presence of two-dimensionally mobile positively charged aqua complexes X+(H2O)?. A feature of Au sol was revealed: the maximum on dependences of y and Nv on the duration of LTT and the linear y-Ne correlation. © Pleiades Publishing, Ltd., 2010.