Inverse gas chromatography has been used to evaluate the adsorption parameters (DeltaH, DeltaS and DeltaG) of some probes, each representing a class of organics (n-hexane, cyclohexane and benzene) on 4A and 13X zeolites. The adsorption parameters of the probes on 4A were determined in the finite concentration region, and those on 13X were determined in the infinite dilution region. The interactions between the probes and the surface were discussed in the light of determined thermodynamic parameters of adsorption. It was found that the adsorption isotherms for 4A conform with the Langmuir equation and benzene exhibits more negative DeltaH than for n-hexane and cyclohexane on both 4A and 13X. Also, interactions of the benzene and n-hexane with 13X were found to be stronger than that on 4A.