Ni-based heat resistant fibres were used for reinforcing AI-based matrices. The goal was to improve the high-temperature mechanical properties of the matrix while keeping a good ductility of the material, thanks to the ductile nature of the fibres. In order to prevent reaction when liquid Al comes into contact with the Ni-based fibres during the processing of the composites by squeeze casting, it was found beneficial to passivate the fibres by oxidation before infiltration. In order to optimise the composite, as far as the oxidation conditions of the fibres are concerned, tensile tests have been performed on composites processed using fibres oxidised during 30 minutes at 600 degreesC, 750 degreesC and 900 degreesC. The best properties were obtained for the intermediate temperature of 750 degreesC. Thus, a compromise was reached between a sufficient roughness and/or an appropriate nature of the interface for good fibre/matrix adhesion and a limited oxidation to prevent degradation of the fibres. Indeed, TEM characterisation of the interfaces revealed the presence of cavities below the surface of the fibres, due to oxidation mechanisms.