In this paper a quantitative study of the adsorption of iso-C4H9CN (isovaleronitrile, IVN) at the interfaces between Hg and In-Ga alloy (eutectic composition) electrodes and aqueous solutions is described. The equilibrium charge densities at Hg electrodes were determined from both electrocapillary and impedance measurements, whereas at the In-Ga electrode only impedance data were available. The adsorption parameters for IVN, including the standard Gibbs energy of adsorption (DeltaG(ads)degrees), the lateral interaction parameter alpha, and the limiting Gibbs surface excess (Gamma(max)), were calculated and compared with previous data relative to the behavior of aliphatic compounds at different interfaces. The experimental results are discussed in terms of metal-solvent and metal-adsorbate interactions.