The use of aluminium alloys in civil engineering is becoming more and more popular. An experimental investigation was performed on aluminium alloy square and rectangular hollow sections subjected to bending. The test program consisted of 11 three-point bending tests and 11 four-point bending tests. The test specimens were fabricated by extrusion using 6061-T6 heat-treated aluminium alloy, and had width-to-thickness ratio ranging from 2.8 to 20.5. The lengths of the beam specimens were 690mm for the three-point bending tests and 990mm for the four-point bending tests. Material properties were obtained from tensile coupon tests and hardness measurements. The available data from previous studies on aluminium simply supported beams of square and rectangular hollow sections were also considered in this study. A comparison of the test strengths with the design strengths calculated from the American, Australian/New Zealand and European specifications for aluminium structures is presented. The test results were also compared with the moment capacities obtained from deformation-based Continuous Strength Method (CSM). It is shown that the design strengths predicted by the three specifications are generally conservative, while the CSM provides a more accurate prediction. This is attributed to the occurrence of strain hardening in stocky cross-sections, which is neglected by the three specifications but allowed for in the CSM.