A general cold-formed steel portal framing system is proposed that uses simple bolted moment connections, formed through brackets, for the joints. Such brackets are easy to manufacture and the joints easy to assemble on site. The joints, however, are semi-rigid and the importance of this for the design of the frame is explored through a combination of numerical analysis and full-scale testing. A simple beam idealisation that accounts for the semi-rigidity of the joints in a frame analysis is described and verified using a combination of finite element shell analysis and laboratory tests. The efficiency of the proposed frame is compared to that of an equivalent rigid-jointed frame, including consideration of serviceability requirements and practical site constraints on the size of the brackets and number of bolts used for the joints. For certain combinations of frame geometry and imposed loading such frames are shown to provide very competitive alternatives to conventional rigid jointed hot-rolled steel construction. J. B. P. Lim, BEng, PhD The Steel Construction Institute, (previously at The University of Nottingham) D. A. Nethercot, BSc(Eng), PhD, DSc, FREng, FIStructE, FICE, FCGI I. C. S. T. M. (previously at The University of Nottingham)