Formation of vanadium silicides by the interactions of vanadium with bare and oxidized Si wafers has been studied by both x‐ray diffraction and He ion backscattering techniques. X‐ray diffraction was used to identify phases and ion backscattering to profile compositional changes. In the case of V on Si, the silicide VSi2, which is a silicon‐rich phase, was found to form at temperatures from 600 to 1000 °C. In the case of V on SiO2, reactions took place only at temperatures above 800 °C, and the reaction products were identified to be V3Si, V5SI3, and V2O5. Both V3Si and V5Si3are vandium‐rich phases, and the V3Si that we found was a continuous layer between the substrate and the other two phases, and became superconducting at about 15 °K.