The interlaminar stresses in a laminated rectangular orthotropic plate with four sides simply supported edges during free vibration was determined by using the integration method involving the dynamic inertia terms and displacements. The approximate stresses solutions are obtained under the effect of frequencies of vibration for four-layer symmetric cross-ply laminates with the ply configurations [0 o /90 o ] s and [90 o /0 o ] s , angle-ply laminates with the ply configuration [45 o /-45 o ] s . Numerical results show that the natural frequency has significant effects on the dominant interlaminar stresses in the stacking sequences [0 o /90 o ] s ,[90 o /0 o ] s and [45 o /-45 o ] s .