The synthesis of ring-opening metathesis polymerization ( ROMP) derived monolithic media prepared from cis-cyclooctene (COE) as monomer, tris(cyclooct-4-ene-1-yloxy) methylsilane ( CL) as cross-linker, toluene as microporogen, and 2-propanol as macroporogen is described. Monolithic supports with varying composition in terms of COE, CL, microporogen, and macroporogen were prepared using RuCl2(Py)(2)(1,3-Mes(2)-imidazolin-2-ylidene)(CHC6H5) (Mes = 2,4,5-trimethylphenyl,Py =pyridine) and pyridine as modulator and characterized via inverse size exclusion chromatography (ISEC) and electron microscopy. Monoliths 3 x 100 mm in size were used for the separation of a mixture of five proteins, i.e., ribonuclease A, lysozyme, insulin, cytochrome c, and myoglobin. Semipreparative separation of these compounds was achieved within less than 150 s by applying gradient elution. Peak half-widths (omega(0.5)) were < 6 s, and resolution (R-s) was > 1.2 throughout. Functionalization of the novel support was accomplished in situ and exemplified by grafting various amounts of 7- oxanorborn-5-ene- 2,3-dicarboxylic anhydride on the monolithic structure. By this approach, carboxylic acid loadings up to 86 mu mol/g, corresponding to 0.71 wt %, were realized.