Structures for use on the Moon and/or Mars face similar requirements and design criteria despite the differences in the corresponding environmental conditions. In both cases, the internal pressure is the dominant load and, therefore, the structure is a pressure vessel. A generic inflatable module is proposed as an efficient and functional structure for a lunar/Martian base. Each module consists of thin membranes supported by an inflated framing system. Module characteristics, including component dimensions, membrane thicknesses and overall mass, are presented.