Hot-rolled structural steel hollow sections typically display largely homogeneous material properties around the cross-section with low residual stresses, due to the uniform cooling pattern associated with the production of uniform sections of constant thickness. This leads to a stress-strain response with a clearly defined yield stress and an extended yield plateau. To examine the behaviour of such members, tests were carried out on hot-rolled structural steel rectangular hollow sections, including material tests and experiments on stub columns, simply supported beams, continuous beams and propped cantilevers. Two wall thicknesses were considered which gave compact cross-sections according to AISC 360-10 (2010), yet most test specimens did not reach their designated plastic design values. Failure by local buckling occurred during the extended material yield plateau, and did not allow for the benefits from strain hardening that are implicitly assumed for the attainment of the plastic moment capacity. Tests on elements in indeterminate configurations showed that system peak loads can occur when some cross-sections are unloading, having already passed their peak moments. Plotting rotation-curvature curves at hinge locations showed that the hinge rotations from an idealized plastic collapse geometry, are proportional to curvatures only during the elastic loading phase. This proportional relationship deteriorated once cross-section yielding had occurred, as curvatures measured by post-yield strain gauges rapidly accelerated when compared to the rotations measured from inclinometers.