Experimental and numerical studies of stainless steel CHS under combined axial load and bending are described in this paper. The experimental programme included material tests and twenty combined loading tests, while the numerical modelling programme comprised a validation study and a parametric study to generate further structural performance data. Both the experimental and numerical results were compared with the strength predictions determined from a series of international design standards. The comparisons revealed that the design standards yield conservative and scattered strength predictions for stainless steel CHS under combined loading, which can be attributed to the neglect of strain hardening in the determination of cross-section resistances and the use of linear interaction formulae. Improved design rules are proposed through extension of the continuous strength method to the case of CHS under combined loading. Comparisons between the proposals and the test and numerical results indicate a high level of accuracy and consistency in the predictions.