This invention relates to a container consisting of a thermoplastic material, with side walls, flat top and bottom panels of which the top panel is provided with at least one fill/drain opening, and with a continuous circumferential carrying and transport rim. For better utilization of pallet space, the container body has an approximately square cross-section with slightly convex lateral surfaces and slightly radiused corners. In order to counteract the inherent tendency of the flat container walls to bulge and buckle, the container body is provided with vertical and/or horizontal reinforcement elements.