Polycrystalline electrodes of copper(I) bromide were investigated at room temperature in aqueous electrolytes. After long-time stabilisation in a 0.001 M CuSO4 solution, an open-circuit potential of about 0.27 V (SHE) was observed. Nonideal interfacial capacitance values were determined from impedance measurements at frequencies between 100 and 1 kHz. From linear Mott-Schottky plots at electrode potentials between 0.2 and 1.0 V (SHE), we concluded that polycrystalline copper(i) bromide is a p-type semiconductor with a flat-band potential of(1.50 +/- 0.05) V (SHE); an acceptor concentration of (2 +/- 1) 10(16) cm(-3) was found.