The invention includes a method of coating a substrate, comprising exposing a substrate to an initiator capable of initiating a graft polymerization reaction on the substrate, to generate reactive radical sites on the surface of the substrate; contacting the substrate with a composition comprising one or more monomers in a medium which has different hydrophilicity compared to the substrate, and grafting monomer molecules onto the substrate by forming covalent bonds between monomer molecules and the substrate at reactive radical sites on the substrate surface. With the invention, novel coated articles can be obtained which are particularly useful as medical products such as catheters.