The invention relates to flexible pipes for transporting cryogenic gas in liquefied form. The pipe is of composite form and comprises an inner pipe adapted to withstand pressure loads and cryogenic temperatures, an outer pipe adapted to withstand tensile axial forces, and a layer of insulating material (34) interposed between the inner and outer pipes. The inner pipe is defined by a hollow carcass (10) formed from a helical interlocked metallic strip (12), the internal and external surfaces of which are lined with a fluid-pressure containment sheath (32) of fully fluorinated fluoroplastic. The insulating layer (34) acts to maintain a temperature differential between the respective pipes. Adjacent portions of the strip (12) in the carcass (10) are moveable relative to each other to provide flexibility to the pipe along its length.