Abstract: For surface modification of natural or synthetic macromolecular substrates, organic compounds are used that have hydrophilic, hydrophobic, oleophobic, ionic and/or cross-linkable groups and that also have groups which are easily convertible to nitrene or carbene, e.g., azide or diazo groups. Such organic compounds are applied to the surface to be modified as a monolayer or oligolayer from a solution thereof and then are photochemically activated. Conditions which cause orientation of the molecule with the azide or diazo group toward the surface of the substrate are advantageous. The other cross-linkable groups may promote diagonal cross-linking of the applied layer.