Electrochemical quartz crystal microbalance experiments at a gold electrode were used to study the classical Belousov-Zhabotinskii (BZ) homogeneous oscillating system. This system involves Ce(III), malonic acid and bromate ions in 1 M sulfuric acid solution. Open circuit, controlled potential, controlled current and cyclic voltammetric experiments were performed. Under open-circuit conditions, during the BZ reaction, oscillations of the gold electrode potential in the range ca. 0.8 to 1.07 V (SCE) with a period about 80 s occurred. They were accompanied by periodic 10-15 ng changes in the electrode mass. During the oscillation, at more positive potentials a decrease in electrode mass occurred while the mass increased at more negative potentials. At a constant applied electrode potential, corresponding to either the upper or the lower limits attained under open-circuit conditions, periodic pulses of cathodic current occurred. The current pulses are accompanied by mass changes. These current pulses occurring either +0.8 or +1.06 V are associated with the reduction of Ce(IV) formed as a result of periodic homogeneous oxidation of Ce(III) by bromate. A continuous decrease in the electrode mass occurred at 1.06 V. A detailed examination of the gold electrode behavior in the solutions containing individual components of the system using cyclic voltammetry and quartz crystal microgravimetry provided the information needed to interpret the mass changes that occur in the oscillating system in terms of bromide ion adsorption and gold dissolution.