The behaviour of cold-formed lean duplex stainless steel sections is investigated. The material properties of high strength cold-formed lean duplex stainless steel square and rectangular hollow sections were examined. Tensile coupons and stub columns were tested for steel for six different sections. TheYoung's moduli, 0.2% proof stresses, tensile strengths, elongation at fracture and the Ramberg-Osgood parameter of lean duplex stainless steel material were measured. The initial local geometric imperfections of the six sections were measured. Residual stresses were measured using the method of sectioning. The membrane and bending residual stress distributions in the cross-section were obtained and plotted. The stub column test strengths obtained from this studyand the available data were also compared with the design strengths predicted by the American Specification, Australian/New Zealand Standard and European Code for stainless steel structures. Generally, the three specifications conservatively predicted the column strengths.