Monolithic capillary columns for hydrophobic interaction chromatography (HIC) have been prepared by thermally initiated, single-step in situ polymerization of mixtures of monovinyl monomers including butyl methacrylate and/or 2-hydroxyethyl methacrylate, with a divinyl crosslinker glycerol dimethacrylate or 1,4-butanediol dimethacrylate using two different porogen systems. Two porogenic solvent mixtures were used; one "hydrophilic", consisting of water, butanediol, and propanol, and one "hydrophobic," comprising dodecanol and cyclohexanol. The porous structures of the monoliths were characterized and their performance was demonstrated with a separation of a mixture of myoglobin, ribonuclease A, and lysozyme under conditions typical of HIC.