The analysis of high performance liquid chromatography (HPLC) traces for the estimation of isotherm type and parameters has been examined. The method employed was to compare HPLC chromatograms for the adsorption of the antibiotic precursor cephalosporin C on macroporous polystyrene Amberlite XAD-2 resin with two theoretical models based on a linear or a Freundlich isotherm. Inter- and intraparticle mass transfer was represented by a lumped overall mass-transfer coefficient using a linear concentration driving force. Isotherm and mass-transfer parameters were varied to obtain optimized fits to experimental chromatograms for a range of liquid flow rates, inlet cephalosporin C concentrations and pH. The Freundlich isotherm parameters so obtained favourably compared with those determined by two different equilibrium techniques to demonstrate the utility of the method for parameter estimation. Sources of error in the analysis procedure are shown to derive partially from the use of a simple mass-transfer model and also from the correlation between pairs of isotherm parameters.