Capacity-potential data for the adsorption of cysteine and other organosulfur compounds on polycrystalline gold are reported. Cysteine, N-acetylcysteamine and cysteinesulfinic acid form monolayers on gold through the thiol group and significantly lower the interfacial capacity in the double-layer region. However, cysteic acid forms multilayers under the same conditions. The surface excess of the compounds at full monolayer coverage has been estimated and compared with the data for the adsorption of simple n-alkylthiols. It is argued that the packing of the cysteine and related compounds is more compact because of strong electrostatic interactions.