Department of Chemistry, Panjab University, Chandigarh Manuscript received 28 January 1974; accepted 11 April 1975 Adsorption isotherms of methanol, ethanol and butanol on casein and its major fractions α-and β-caseins have been reported and analysed by B. E. T. as well as Harkins and Jura treatments. The values for specific surface area, as obtained from the above two techniques as well as from the knee of the isotherm of a given adsorbate, are in fair agreement but fall with increase in molecular dimensions of the adsorbate. The t-plots of the systems indicate that casein and its fractions contain micropores of width varying between 11.7 and 14.8 l.. The pores are too small to be easily accessible to butanol molecules. The differential free energy, enthalpy and entropy changes for different surface coverages by each adsorbate have been calculated. These quantities show an abrupt fall on the completion of the monolayer.