AbstractÐClosed-cell aluminium alloy foams exhibit exceptional resistance to ®re. It is unclear why this happens, although the protection imparted by oxide Al 2 O 3 layers has been suggested. This work attempts to uncover the thermal transport processes in metallic foams. The apparent thermal conductivities of twodimensional foams having a variety of cellular microstructures are ®rst calculated. These include regular honeycombs, Voronoi structures and Johnson±Mehl models. The eects of several types of geometric imperfectionÐPlateau borders, cell-edge misalignments, fractured cell edges, missing cells, inclusions and cell size variationsÐare studied by using analytical as well as ®nite element methods. The focus is on metallic foams where the transport of heat is dominated by solid conduction and thermal radiation; contributions from gaseous conduction and convection are neglected. The coupling of solid conduction with thermal radiation is dealt with by using the method of ®nite elements. These results are then applied to solve the transient temperature ®eld of a cellular metal plate subjected to a sudden introduction of a hightemperature source of heat such as ®re. The factors which dictate the thermal and structural ®re retardance of cellular metallic foams are identi®ed.