The linear stability theory is used to investigate analytically the possibility of the motionless basic state in a porous layer heated from above and subjected to vibration. The linear stability results presented for the specific case of low amplitude vibration shows that there exists a bandwidth of frequencies for which the convection in a porous layer with a stable density gradient can be destabilized. In addition the scaled Darcy-Prandt1 number is shown to influence the onset of the subharmonic and synchronous solutions.