Abstract: A modular panel system for use in constructing temporary buildings of the type that can be disassembled and transported in disassembled form for erection at a new site. Each panel includes a ribbed sheet of steel secured to a rectangular frame formed by three steel angle members and a channel. The ribs on each panel provide ridges on the outwardly facing surface of the sheet and corresponding grooves on the inwardly facing surface. The panels are bolted together with one rib of each panel closely overlapping one rib of the adjacent panel to provide watertight joints between all panels on the walls and roof of the building. The construction of the panels permits them to be compactly stacked for storage and transport.