[en] A capacitance probe apparatus is described which was used to detect the deflection occurring during ion implantation of thin specimens of annealed steel. The deflection is related to the introduction of a surface compressive stress. 100-keV argon ion implantation is found to produce surface stresses of several thousand lbs/in.² which reach a maximum at a dose approximately 5.0 x 10¹⁶ ions-cm^-2. Light ions, such as nitrogen, which form chemically stable compounds within the steel, generate similar stresses within the surface such that a macroscopic deflection of the specimen can be observed. In this case very high doses are required to maximize the stress (approximately 10¹⁷ ions-cm^-2 Results are interpreted with reference to damage mechanisms and nitride formation, and are discussed in relation to the mechanical property changes previously reported. (U.S.)