Through a programme of experiments, numerical modelling and parametric studies, the implications of allowing for strain-hardening in the design of partially restrained steel beams are investigated. A total of fourteen tests were performed on simply supported beams that were partially restrained against lateral torsional buckling. Four different restraint spacings were considered in the tests to give non-dimensional lateral torsional slenderness values of 0.1, 0.2, 0.3 and 0.4 for the unrestrained lengths. In all tests, bending resistances in excess of the plastic moment capacity were observed, but in order to attain the levels of resistance predicted by the continuous strength method (CSM), which allows for strain-hardening, closer restraint spacing than the minimum specified by EN 1993-1-1 (2005) is required. Using additional data generated as part of an analytical and numerical study, as well as test data collected from the literature, a basic design approach was presented that incorporated a limiting lateral torsional slenderness for the CSM of 0.2, as well as a simple transition function from bending resistances predicted by plastic theory to those predicted by the CSM.