Potential applications of a very general route to photochemically modifying a range of surfaces will be described. Surfaces which have been modified vary considerably and include polyimide, polyethylene, fluoropolymers, polyester, glass, tin oxide and aluminum. Photoactivated azides, for example 3-azidopyridine, have been found to be very effective at modifying a range of surfaces. Using this method organic type functional groups, in this case pyridine type groups, can be photografted on to the surface. As a result of photomodification the surface properties change. In the case of polyethylene for example the surface becomes more hyrophilic and shows improved adhesion to metals. These modified surfaces also display acid-base character. In the protonated form anions can be exchanged into the film. This method has been used to modify a metal oxide electrode surface to develop chemically modified electrodes. The process may also be used in lithography.