In this paper the use of symmetries in problems concerned with laminated fibre-reinforced composite structures is examined systematically. Incorrect and incomplete treatments of this subject have appeared in the literature and these are clarified herein. A model of a complete structure is not needed provided that the geometry and the loading of the structure show the required symmetry properties, even though the boundary conditions introduced can vary from one symmetry to another. The extent of the reduction in the size of the problem depends upon the laminate layout scheme. Particular comments are made on the proper use of symmetries in geometrically nonlinear problems. Further applications of symmetries in analytical approaches which lead to a reduction in the number of the dimensions of the problem are also discussed.