Reissner's, stress-based, shear deformation plate theory is chosen to approximate the stress field for balanced symmetric laminates. The longitudinal stresses are assumed to vary linearly along the plate thickness. In fact, we may view the purpose of this work as an examination of effectiveness of mathematical laminate models in which the response is defined in terms of force and moment resultants. Average stiffness moduli are considered to characterize the laminate properties. The accuracy and the range of application of the present approach are proved for laminated plate:1- in cylindrical bending and 2-simplly-supported with different thickness, for which elasticity solutions exist. The paper presents the first step of validation of the developed theory. The cylindrical bending of symmetric cross-ply laminated plates subjected to sinusoidal loading is investigated. Results from the present theory are compared with those from exact solutions and other known theories as well.