Abstract: A fire resistant structure, and in particular a fire door leaf, having no components of asbestos material, and comprising a sub-frame consisting of two spaced apart arrangements of sub-frame members between which a central panel in the form of a glass fiber reinforced gypsum sheet is attached and two other panels of high density compressed timber fiber board being attached to the sub-frame members on opposite sides of the structure to define, with the central panel, spaces in which insulating material in the form of mineral fiber batts is positioned, with the structure being completed on both faces by panels of sheet steel or wood veneer.