The electrochemical behaviour of a copper electrode in ammonium sulphide solutions was studied using cyclic voltammogrammetry and potentiostatic and galvanostatic polarization techniques. The morphology and composition of the layers formed on the copper electrode were studied by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) and X-ray powder diffractometry. Besides different binary copper sulphide phases the ternary phases NH4Cu7-xS4 and NH4CuS4 were observed, NH4Cu7-xS4 crystallizing as needles perpendicular to the electrode surface.