Many factors influence the design of a containment structure: size and shape of the reactor and other equipment to be housed, topographic and subsurface features of the site, proximity to populated areas, relative economy of construction materials, need for access during operation, and most important, pressure-volume duty. For a given duty, and for geometrically similar structures, the volume can often be varied over a broad range with little change in total cost. The upper limiting volume is reached when external forces rather than internal govern the design; the lower limit is usually the point where the membrane becomes unreasonably thick. Two or more small vessels connected together may have advantages over one large vessel, but additional design problems arise in making them act as a unit. The merits of total versus partial containment are discussed. A comparison is made of the various designs studied in selecting the containment vessel for the Dresden Nuclear Power Station. These included simple and composite structures, some above and some below ground, some designed for total and some for partial containment. A steel sphere for partial containment was selected as best suiting the needs of this project.