This study has described a detailed investigation into the structural and thermal behaviour of cold-formed light gauge steel frame (LSF) load-bearing wall panels lined with gypsum plasterboards subject to standard fire conditions. It included both the conventional steel wall systems with and without cavity insulation as well as a new steel wall system based on a composite panel in which a layer of external insulation was used between two plasterboards. Both full scale fire tests and extensive numerical studies were conducted on a series of LSF load-bearing wall panels under fire conditions. This research has thus developed comprehensive experimental and numerical data for both the conventional and the new load-bearing cold-formed steel wall systems under fire conditions including simple and accurate methods to predict their fire resistance rating. It has considerably improved the knowledge and understanding of the fire performance of LSF wall systems under fire conditions, and has led to the development of both accurate design methods for fire conditions and new LSF wall systems with increased fire resistance rating.