Dynamic responses of discretely stiffened composite flat panels are studied in this paper by using the transfer matrix method. Transfer matrices are derived from the governing equations of composite panel and stringer. Numerical computations are performed for a simplified structure model containing two or three panel bays subjected to uniformly distributed white noise pressure. Numerical results include natural frequencies, deflection and stress response spectral densities of stiffened panels and their root-mean-square values. Effects of fiber orientation in composite panels and stringers are investigated.