This paper describes an experimental study on the influence of kinetic energy in surface ionization, using a Re oxide surface with accelerated benzene or toluene molecules. These fast molecules in seeded supersonic molecular beams from a nozzle interact with a metal surface. Results are obtained as a function of incident kinetic energy and system parameters, indicating that kinetic energy causes the surface ionization to increase drastically above threshold energy. The threshold kinetic energy, which varied with the surface temperature (T-s), was around 3.0 eV for benzene, when T-s = 1190 K.