Abstract.The 24Mg(, p)27 Al nuclear reaction was applied for the determination of the magnesium distribution in near-surface layers of materials. The cross sections of this reaction were determined in the energy region between 4.5 and 5.5MeV in steps of 5 to 10KeV (lab : 158) using thin magnesium films. The investigated projectile energy region included five main resonances allowing the determination of magnesium. The uncertainty of the cross-section determination was of the order of 7%. The applicability of the technique was tested using Mg-implanted AISI 321 steel samples. Depth resolution of 100nm and detection limits of the order of 0.1ppm were achieved for the determination of magnesium in steel samples using the 4805keV resonance of the 24Mg(, p)27 Al nuclear reaction. The shape and height of the magnesium depth-profile in the Mg-implanted steel samples were compared with corresponding values obtained by X-ray photoelectron spectroscopy.