The adsorption of a model amine drug (tacrine hydrochloride) from aqueous solution onto 21 microcrystalline cellulose (MCC) based samples has been investigated. The MCC source (manufacturer) affected adsorption. The adsorption appeared to be fully reversible. Adsorption was reduced by the use of high-density grade MCC, high-energy milling, and silicification. Adsorption of the model drug was not affected by the particle size of the MCC. Significant variations of the adsorption characteristics between batches of certain MCC products were found. The primary mode of adsorption was by ion exchange.