In resisting lateral forces, X-bracings are considered very effective for high-rise frames. As an extension of earlier work of vibration of X-braced portal frames, in-plane vibrations of N-story X-braced frames are investigated. The elements of such a frame are made of elastic continuum undergoing transverse as well as axial vibrations. The characteristics of X-braced frames are investigated by six sets of numerical examples including free and forced vibrations, and dynamic responses of ground motion.