Electrochemical behavior of the water-soluble C-60-gamma-CD (1:2) inclusion complex has been studied on the hanging mercury drop electrode. A one-electron reversible adsorptive electro-reduction and three irreversible adsorptive electro-reductions were detected by cyclic voltammetry. The amount of C-60-gamma-CD adsorbed at saturation is 2.50 x 10(-11) mol cm(-2), the diffusion coefficient is 4.36 x 10(-6) cm(2) s(-1) and the standard rate constant of the surface reaction k(s) are 0.745 s(-1), 0.612 s(-1) and 0.513 s(-1), respectively.