Adsorption of beta-cyclodextrin results in the formation of compact layers which cover the mercury electrode interface by the nucleation and growth mechanism. Ac. measurements of admittance versus time were used to identify the growth mechanism. Unlike simpler systems, the present case cannot be described by the Avrami formalism because of a mixed growth mode over almost the entire adsorption regions. Measurements at positive potentials (from 0 to + 0.2 V vs. Ag/AgCl) over long times reveal growth proceeding in the island mode and undergoing instantaneous nucleation in the first and the second layers.