The high temperature oxidation of ion-implanted titanium was studied using the scanning electron microscopy, X-ray photoelectron spectroscopy and Rutherford back-scattering techniques. The specimens were implanted with either tin ions (Sn+) or nitrogen ions (N2+) or a combination of the two, to doses of between 1015 and 1017 ions cm-2. The implantation energies were 200 keV for tin ions and 200 or 400 keV for nitrogen ions. The specimens, treated and untreated, were oxidized in air at 500 °C for 100 h. The combination of nitrogen and tin ions was found to increase the thickness of the nitride-oxide film on the titanium surface by four orders of magnitude and to increase the hardness significantly. Nitrogen ions alone produced a more uniform oxide layer but the thickness of the layer was unchanged. The implantation of tin ions alone led to a reduction in the oxidation of titanium by the formation of SnO2. The results are discussed in terms of well-established mechanisms of the oxidation of titanium, in which oxygen diffuses into the metal along anion vacancies of the rutile lattice. © 1987.