The effect of three different electrolytes on the efficiency of polypyrrole deposition was studied using Rutherford backscattering spectrometry (RBS). The RBS results were used to determine the thickness, roughness, and composition of the polypyrrole films. The films were deposited from aqueous solutions of sodium perchlorate, sodium xylene-sulfonate, and poly(sodium 4-styrene-sulfonate) (NaPSS). The highest deposition efficiency (93%) was obtained with the sodium xylene-sulfonate electrolyte. The NaPSS electrolyte yielded the highest film density (1.55 g/cm(3)) and the lowest film roughness. Deposition from NaClO4 electrolytes yielded the lowest efficiency and the roughest films. Evidence for a nucleation and growth mechanism was also observed.