Current design guidance on stainless steel structures is largely based on assumed analogies with carbon steel, thereby neglecting stainless steels* actual material behaviour in favour of simplicity. However, its high initial cost warrants the development of improved design guidance which is rational, safe, efficient and in accordance with the actual nonlinear material behaviour. Within the current research project, all reported test data on stainless steel cross- sections (beams and stub columns) have been gathered and utilized to update current European design guidance and to propose alternative novel design methods which account for actual material behaviour and allow for more efficient material use. Existing design methods which allow for the effect of element interaction on cross- section capacity of carbon steel plated sections have been adapted to stainless steel and a modification to the continuous strength method has been proposed, which leads to a significant decrease in the scatter of the predictions. Moreover, the possibility of expanding the scope of the current codified provisions of Eurocode 3: Part 1-4 to new material grades and cross-sections has been investigated through experimental and numerical studies. A series of tests and finite element (FE) analyses on stainless steel Oval Hollow Section (OHS) members was carried out to investigate the structural behaviour of these sections. Similarly, experimental and numerical studies on a new grade of stainless steel with a low nickel content, termed lean duplex stainless steel (EN 1.4162) were also conducted and its applicability for structural applications was verified. Finally, a series of tests on continuous stainless steel beams has been undertaken to investigate the effect of moment redistribution on the capacity of indeterminate stainless steel structures and assess the applicability of nonlinear structural analysis procedures, equivalent to the plastic design of carbon steel structures, to indeterminate stainless steel structures. It was found that plastic design can be safely applied to stainless steel structures and an extension to the continuous strength method has been proposed.