The adsorption parameters (alpha, with respect to polystyrene) for 20 cyclic aliphatic ethers were established experimentally in the usual way. Among this set of ethers are members from three cyclic structural categories, namely, the polymethylene oxides [(CH2)(n)O; n = 2-9], the polymethylene formals [(CH2)(n)OCH2O; n = 2-11], and the polyethylene oxides [(CH2CH2O)(e); e = 1-5], and some of the corresponding methyl or gem-dimethyl modifications thereof. The data obtained thereby were used to establish the log alpha vs N linear relationships (eq 1) for each of the subsets of homologous series contained in each of these structural categories, as described in the text. These linear relationships were then used to calculate the alpha-values for the many remaining members that are not yet available for experimental measurement in our laboratory. The results obtained thereby show that the alpha-values fur the cyclic ethers in a given homologous series are uniformly greater than those for the corresponding set of acyclic ethers. They also confirm that methyl groups have a marked negative effect on alpha when positioned on the carbon atoms adjacent to the adsorbed ether oxygen atom, but they have the opposite effect when located one or more carbon atoms removed from adjacency. The magnitude of this positive effect appears to increase with the distance from the adsorption site. These observations parallel those observed in our earlier studies involving the corresponding acyclic aliphatic ethers.