The adsorption of ethylxanthate upon copper sulfide has been studied by electrochemical impedance spectroscopy. Prior to each experiment being performed, the copper sulfide composition was fixed by imposing a constant potential. The spectra with and without ethylxanthate in the solution show no difference below the potential threshold. but above this potential the spectra differed dramatically. The shapes of the impedance: diagrams were interpreted by Formation of a bilayer structure at the surface of the mineral which develops in two steps at the same potential. The first lever corresponds to a chemisorbed layer while the porous second layer comprises copper xanthate. An explanation for the suppressor effects of the HS- anions is also given in terms of the redox potential For the Cu2-xS/HS- redox couple.