The torsional behaviour of cambered plates has been analysed. Plates cambered in one plane change shape when they are twisted. Some oblique sections are flattened out while others are cambered further, and this results in asymmetric behaviour; cambered plates will twist and bend more easily when pushed on their convex surface than on their concave surface. Of the plates which are cambered in two planes, saddle-shaped plates are already flattened in oblique planes; consequently, they will exhibit lower torsional rigidity than dome-shaped plates but will be less susceptible to damage caused by buckling of their edges. These results shed light on the mechanical behaviour of cambered insect wings and feather barbs, and the design of the leaves of grasses and sedges.