Abstract: Laminated beam theory is the basis of mechanical behavior analyses of composite laminated beams and stiffened laminated structures. The first-order shear deformation theories of a transversely laminated beam a longitudinally laminated beam and a combined beam are developed based on the hlindl in hypothesis.The coupled effects between. variables are included in the present theories.The exact stiffness can be obtained by using the stiffness expressions developed.For generality,thermal behavior is considered in the formulation.