This thesis examines the effects of cold forming on the material properties of steel and stainless steel structural members. Extensive research has been carried out over many years on both of these materials as they are used to manufacture structural sections to various design specifications which exist in many different countries. However, to date, no design code exists in the UK for cold formed stainless steel structural members. A significant amount of research has focused on the localised effect of cold forming on material properties such as the yield and ultimate tensile strengths, particularly of steel, and this is discussed at length in Chapter 1- Literature Review. Less attention has been placed on stainless steel, but over the last 20 years with the advent of design specifications particularly in the USA, stainless steel has gained popularity for cold forming. Chapter 1 describes the research that has been carried out on stainless steel, with particular emphasis on localised forming effects. Chapter 2 gives a general introduction to Thin-Walled Structures since cold-formed structural sections are commonly used as thin-walled members. The deformation and properties of metallic materials are described in Chapter 3 showing the particular relevance to the cold forming process. This chapter is extended into Chapter 4 where the strengthening, forming and properties of metallic materials are discussed in detail, with particular attention given to the cold forming processes. Chapter 5 describes existing analytical and design code approaches to determine the increase in strength of cold formed steel structural sections, along with an empirically derived relationship to calculate the increased yield strength of stainless steel sections. Chapter 6 describes the recommendations provided by various design specifications on evaluation of the axial compression capacity of short struts subject to varying degrees of cold forming. This chapter also describes the recommendations provided by various design specifications on evaluation of both the axial compression and the combined bending and axial compression load capacities of cold formed lipped channel section stainless steel columns of short-to-medium length. The results obtained from Chapters 5 and 6 are compared to the results obtained from an extensive experimental approach as described in Chapter 7. A finite element non-linear analysis using the ANSYS finite element software package is presented in Chapter 8 which models the behaviour of cold formed stainless steel lipped channel section columns of short-to-medium length subject to pure axial compression loading and also combined bending and axial compression loading. Chapter 9 presents the experimental findings showing the relationship between material hardness and material yield strength for cold-formed areas. The results are then compared to the theoretical results from Chapter 6 to determine their accuracy in prediction of the structural behaviour of full cold formed structural member cross-sections. The load capacity obtained for axially compressed steel and stainless steel struts from experiments are compared to those obtained from the various design code predictions described in Chapter 6. Also presented are the experimental findings, design code recommendations and finite element predictions for the load capacity of stainless steel columns. Chapter 10 concludes on the work by discussing the various issues arising from the experiments, from the design code recommendations and from finite element analysis 11 M. Macdonald