Abstract: A floor system for a trailer or the like comprising a plurality of elongate sheet metal floor panels extending side-by-side lengthwise of the trailer on beams extending transversely of the trailer. Each of the metal floor panels comprises upper and lower panel members, the upper member being in the form of a shallow inverted channel, comprising a relatively wide web member, a pair of relatively narrow flanges extending down from the web member at opposite sides of the web member, and a pair of fastening lips extending laterally outwardly from the flanges at the lower edges of the flanges and bearing on the beams of the trailer. The elongate metal floor panels are mounted on the beams one alongside another with the fastening lips at adjacent sides of adjacent floor panels defining, in conjunction with the opposing flanges extending up from the fastening lips, upwardly opening generally rectangular recesses extending longitudinally of the trailer between adjacent floor panels.