[en] Nickel-20 wt percent chromium alloys containing ThO₂, Y₂O₃, La₂O₃, Al₂O₃, and Li₂O, as prepared by the mechanical alloying technique, were examined for isothermal and cyclic oxidation resistance in dry air at 1000, 1100, and 1200⁰C. TDNiCr, a commercial electrical heating element alloy (Com Ni--20Cr) and a laboratory melted alloy (Lab Ni--20Cr) were also tested. It was found that Y₂O₃, La₂O₃, Al₂O₃, and ThO₂ dispersoids markedly increased both isothermal and cyclic oxidation resistance compared with Lab Ni--20Cr at all temperatures; in contrast Li₂O additions gave no improvement in protection. Com Ni--20C r was in between Lab Ni--20Cr and the Y₂O₃, Al₂O₃, and ThO₂ containing alloys in both cyclic and isothermal oxidation performance. A mechanism based on alterations in the defect structure of Cr₂O₃ is proposed to explain these dispersed oxide effects on isothermal oxidation behavior. It is based on a reduction in cation transport rates which in turn alter the rate of oxide growth. ThO₂-containing alloys fabricated by the mechanical alloying technique were found to have oxidation resistance fully equal to commercial TDNiCr. Com Ni--20Cr performed better than Lab Ni--20Cr, but not as well as TDNiCr