In this study Nextel 440 type alumina fibre reinforced aluminium matrix composite wires were investigated. Composite wires produced using the continuous process are suitable to simplify the introduction of fibre reinforcements into aluminium castings as well as the production of double composite, sandwich and preferentially reinforced structures. This paper focuses on the porosity of composite wires because minimizing porosity is the primary condition of good mechanical properties. Composite wires were produced with different infiltration pressure (0.83 MPa, 1.03 MPa, 1.24 MPa, 1.52 MPa, and 1.65 MPa) to determine the correlation between infiltration pressure and the porosity of wires. 10 grinded cross-sectional samples were made from each type of composite wires. Based on the micrographs of these samples the volume fraction of aluminium was determined by image analysis, which also yielded information on the porosity of wires. The results show that there is direct (linear) correlation between the infiltration pressure and the decrease in porosity. These findings, however, are valid only for the investigated range of pressure. The measured values were in good agreement with the theoretical model used for comparison.