We have modified the surface of hydrophilic silicon oxide by chemically anchoring an organic monolayer bearing terminal phosphorylcholine (PC) groups and subsequently characterized the structure of the PC layers and their effectiveness in inhibiting the deposition of a range of model proteins. The PC compound was synthesized through coupling of S-aminopropyl trimethoxysilane with acryloyloxyethylphosphorylcholine in 2-propanol. The presence of the labile hydrogen on the secondary amine group of the monomer allowed a subsequent coupling of two monomers with a bridging spacer such as a diisocyanate to form a dimer. The PC dimer was coated onto a silicon substrate via dip coating, and the chemical grafting with the substrate was strengthened by annealing the coated layers at 150 degreesC under vacuum. Neutron reflection measurements showed that upon the formation of a well-packed monolayer, the small PC molecular coatings were as effective as the PC polymer coatings in reducing protein adsorption in vitro.