A window frame section (100) comprises a central portion (10) of a thermally-insulating material and inner and outer sections (20, 30) of a different material, such as steel, the central portion (10) being produced by extrusion or pultrusion and incorporating projections and channels for receiving glazing units, beads and hardware fixings. The inner and outer faces of portion (10) have angled ends (12, 14, 17, 19) for the attachment of the sections (20, 30). Portion (10) may be hollow and may comprise a plurality of hollow channels. Portions (20, 30) may be attached to central portion (10) by retaining pins.