The relative sensitivity factors (RSFs) of aluminum in glow discharge mass spectrometry have been investigated. The RSFs of Al in Fe, Ni, Cu and Ti-based metals have been determined at different concentrations. The RSFs of Al depend on the concentration. These are larger for larger concentrations. On the other hand, the RSFs of Fe, Ni, Cu and Ti do not show such a clear dependence on the concentration as Al. The present results will be discussed in connection with the previous observation that the RSFs of Al in the case of the matrix are larger compared with the RSFs of small components.