The adsorptive accumulation of cercosporin (CER) at glassy carbon electrodes is studied by square-wave voltammetry (SWV). The Freundlich adsorption isotherm resulted in being the best one to describe the specific interaction of CER with glassy carbon electrodes by using a fitting procedure of experimental fractional surface coverage vs. the CER bulk concentration (c* CER ). SWV was also used to generate Q vs. c* CER and I p, n . vs. c* CER calibration plots from pure commercial reagent solutions. Theoretical detection limits of 1.8 Â 10 À7 and 9.7 Â 10 À8 M were calculated from Q. vs. c* CER and I p, n vs. c* CER plots, respectively. The lowest concentration value measured experimentally from calibration plots performed at a f 40 Hz for a signal to noise ratio of 2 : 1 was 3.7 Â 10 À8 M, being this value two orders of magnitude smaller than that obtained previously by us from the diffusion controlled CER reduction peak. I p, n ./f vs. f plots from SW voltammograms performed at different c* CER as well as different accumulation times showed the so-called ™quasi-reversible maxima∫. A splitting of the voltammetric peak was also observed by increasing the SW amplitude at a given frequency. A value of ( À 0.260 AE 0.011) V was determined for the formal potential of the adsorbed redox couple from the split voltammetric peak. A full characterization of the surface redox process was obtained by applying the methods of the ™quasi-reversible maximum∫ and the ™split SW peak∫. In 1 M HClO 4 aqueous solution, the formal rate constant and the anodic transfer coefficient were (3.5 AE 0.5) Â 10 2 s À1 and (0.50 AE 0.03), respectively. Besides, the number of electrons exchanged during the redox reaction was calculated as n % 1.