The adsorption kinetics of asphaltenes at the toluene-silica interface has been measured for nine solution concentrations C-S (from 5 to 3000 mgL(-1)) Results could be adjusted to an irreversible second-order adsorption kinetics, where the adsorption rate k was strongly dependent on concentration. Thus a large reduction in k was observed when C-S was increased in the studied concentration range. This rate reduction was accounted for in terms of adsorption of aggregates formed in solution. The step-wise trends observed for the adsorption isotherms of asphaltenes on mineral surfaces, could be reproduced using the above k values.