Monosized-porous polymethacrylate based hydrophilic microspheres with reactive chloropropyl functionality were produced as a starting material for the synthesis of an octadecylated stationary phase for microbore-reversed phase chromatography. A seeded polymerization method based on a new functional monomer, 3-chloro-2-hydroxypropyl methacrylate (HPMA-Cl), was used with a methacrylic crosslinking agent, ethylene dimethacrylate (EDMA). The presence of a reactive functionality (i.e. chloropropyl moiety) in the poly(HPMA-Cl-co-EDMA) microspheres allowed the covalent attachment of a hydrophobic ligand, octadecylamine (ODA), onto the particles via a single stage nucleophilic substitution reaction. ODA-attached poly(HPMA-Cl-co-EDMA) microspheres were slurry packed into a microbore column. Alkylbenzenes and phenols were successfully separated with the theoretical plate numbers up to 60 000 plates per m. ODA-attached poly(HPMA-Cl-co-EDMA) microspheres are good candidates to be an alternative column packing material to the currently available packings for microbore-reversed phase chromatography (mu-RPLC).