The relationships between alloy microstructure and air oxidation kinetics and alloy microstructure and microhardness in the Al-Ti-Cr system for exposures at 800°C and 1000°C were investigated. The relevant phases were identified as τ (Ll2), γ (Ll0), r-Al2Ti, TiCrAl (laves), and Cr2Al. Protective alumina formation was associated with τ, Al-rich TiCrAl, and γ/TiCrAl mixtures. Brittleness was associated with the TiCrAl phase and τ decomposition to Al2Ti + Cr2Al. It was concluded that two-phase γ + TiCrAl alloys offer the greatest potential for oxidation resistance and room temperature ductility in the Al-Ti-Cr system.