The relationship between microstructure, coefficient of friction and wear behaviour against mild steel has been examined for three commercially extruded high-tensile brasses, containing additions of manganese (similar to 3 wt%) and silicon (similar to 1 wt%). The alloys contained an approximately constant volume fraction of Mn5Si3 (6-7%) but the proportions of the alpha and beta phases present were varied widely both by heat treatment and by changing the composition, particularly the aluminium content which lay in the range 0-3 wt%. A conventional pin-on-rotating-disc configuration with different loads and sliding speeds was used to determine the wear and the coefficient of friction. The effect of heat treatment on the wear behaviour of given alloys was complex, and depended on the volume fraction of the alpha and beta phases, on their distribution in the microstructure, and on the ease with which the hard Mn5Si3 particles became detached from the phases in which they were located. The average coefficient of friction for the materials examined was 0.36 +/- 0.02 and showed little variation with composition and microstructure, but it was clear that the experimental data was being influenced by detachment of Mn5Si3 particles. Results for the three alloys examined are presented and discussed.