Abstract: The invention relates to a process for making the surface of polymeric substrates hydrophilic, which includes coating the surface of a polymeric substrate with a solution of a macroinitiator, wherein the macroinitiator includes a polymer framework and side chains attached to the polymer framework, and wherein at least one of the side chains includes at least one free-radical-forming group. Optionally, a hydrophilic vinyl monomer or monomers may then be free-radical polymerized or graft polymerized onto the macroinitiator-coated substrate. A crosslinking vinyl monomer may optionally be used together with the macroinitiator or the hydrophilic vinyl monomer. The invention also relates to polymeric substrates having hydrophilic surfaces obtained by the process, and articles that include the hydrophilic polymeric substrates.