Infinite-dilution activity coefficients for nine classes of volatile organic compounds (paraffins, olefins, cycloparaffins, aromatics, ketones, nitriles, alcohols, esters, and chlorocompounds) in a series of four cyclic olefin copolymers were determined using an inverse gas chromatography technique with a packed column. Abraham's equation of solvation was used for the evaluation of the different types of interactions between the solvents and polymers. The results are compared with the activity coefficients at infinite dilution obtained for other polymers of similar use.