TiAlN films were deposited on tool materials through an r.f. bias reactive sputtering process. The effects of the aluminium composition in the films on the hardness, oxidation resistance and wear properties were studied. The results indicated that both the aluminium composition and cutting speed had substantial effects on wear resistance. The oxide phases formed at elevated cutting temperatures, especially alumina, had important effects on the cutting performance. An optimum improvement of nine times in wear resistance compared to uncoated tools, was observed.