This study was designed to answer the question whether the chromatographic performance of porous polymers — serving here as a model system for pressure-sensitive separation media of relatively large mass transfer resistance — could be improved (a) by imposing on them a chromatographically favorable, extrinsic macrostructure and (b) by protecting that macrostructure against physical deformation. Packed-column gas chromatography was used as the test system.Protected porous polymers (PPP's) were synthesized from pure divinylbenzene (DVB) inside conventional diatomaceous supports, using various amounts and types of porogens. The non-extractable polymer loads ranged from 10 to 40% and conformed to (i.e. formed layers on) the diatomaceous macrostructures. The best plate numbers were in excess of 4000/m on a 100/120 mesh Chromosorb W base. The mass transfer resistance of these materials was very low and permitted high flow rates. The PPP's could be used up to 280 °C and did not appear to suffer deformation; in fact, the polymer appeared to shield the diatom supports from abrasion. The data indicate that the porous polymer deposits had relatively high specific surface areas, and produced a relatively large value for the free energy of sorption per methylene group, as compared with conventional porous polymer beads. Otherwise, protected and unprotected types of porous polymers had similar chromatographic characteristics. Keywords: porous polymer, poly(divinylbenzene), gas chromatography, protected polymer, diatoms.