The rotating tapered laminated composite beams are basic structural components when dealing with a variety of engineering structures such as airplane wings, helicopter blades and turbine blades as well as many others in the aerospace, mechanical industries. The great possibilities provided by composite materials can be used to alter or change favorably the response characteristics of structures. Due to the outstanding engineering properties, such as high strength-to-weight and stiffness-to-weight ratios, the composite beam structures are likely to play a significant role in the design of structures when the weight and strength are of primary consideration. The behavior of composite beam structures can also be effectively and efficiently tailored by changing the lay-up parameters. The analysis of composite beams is, of course, significantly more difficult than that of metallic counterparts.An important element in the dynamic analysis of composite beams is the computation of their natural frequencies and mode shapes. This is important as the composite beam structures often operate in complex environmental conditions and are frequently exposed to a variety of dynamic excitations. The characteristics of rotating flexible structures differ significantly from those of non-rotating flexible structures. Centrifugal inertia force due to rotational motion causes the variation of ending stiffness, which naturally results in the variations of natural frequencies and mode shapes. Moreover, the stiffness property of composite structures can be easily modulated through changing their fiber orientation angles and number of layers.The finite element method (FEM) is one of the most powerful numerical procedures for solving the mathematical problems of engineering and physics. Nowadays, some advanced formulation have been introduced, among them is the hierarchical FEM (HFEM). In conventional FEM, a beam element is modeled using two nodes at the end. Therefore, a large number of elements are needed to achieve an acceptable accuracy. In HFEM, some polynomial or trigonometric terms are added to the displacement and rotation function in order to obtain extra degrees of freedom. Thus, the same accuracy can be achieved by using much less number of elements. This results in rapid convergence. In this thesis, a hierarchical finite element technique is applied to find the natural frequencies and mode shapes of composite beams in the bending mode of vibration by taking into account the taper and the rotation simultaneously. The element mass and stiffness matrices are derived and the effects of offset, rotation, taper ratio and shear deformation on the beam natural frequencies are investigated. Key words: Vibration, Tapered Composite Beam, Hierarchical FEM, Rotating.