Various crosslinked poly(4-vinylpyridines) having different degrees of crosslinking were prepared by radical copolymerization of 4-vinylpyridine with divinylbenzene as a crosslinker. The abilities of these crosslinked polymers to bind ethyl orange and propyl orange were investigated at various temperatures in a buffer solution of pH7. From the equilibrium binding amounts, the first binding constants against the temperatures showed bell-shaped curves. This result was attributed to both the suitable crosslinked hole sizes of the polymers and the hydrophobicity of the binding systems. The first binding constants and the temperatures of maximum binding of these binding systems were observed to be lower than those of previous binding systems, 4-vinylpyridine-N,N'-methylenebisacrylamide copolymers-the homologs of methyl orange. These results were discussed in terms of hydrophobicity and rigidity of benzene ring which was used as the crosslinker in the crosslinked poly(4-vinylpyridines).