The static and dynamic behavior of composite box beams is investigated using a large deflection beam theory. The finite element equations of motion for beams undergoing arbitrary large displacements and rotations, but small strains, are obtained from Hamilton's principle. The importance of non-classical structural phenomena is systematically investigated for composite box beams. The sectional elastic constants including warping deformations have been determined from the refined cross-sectional finite element method. The effects of fiber orientations and stacking sequences on the static deformation and vibration characteristics have been investigated. Numerical results are compared with the previously published experimental and theoretical results. The present results are proved to be very accurate.