In the aerospace industry, there is an ever present need to detect fatigue in structural materials. For instance, the ability to detect serious plastic deformation in landing gear materials is highly desirable. Since most landing gear are composed of ferromagnetic materials, the nondestructive methods of testing are limited. The procedure chosen for this investigation is monitoring the Barkhausen effect, with the criteria for instrumentation choice being portable and easy to use. The Rollscan 100–2, designed and manufactured by American Stress Technologies, Inc., met the criteria (Figure 1). Internal stress measurement using this instrument is based on the principle of magnetoelastic interaction between magnetostrictive and elastic lattice strains [1]. The Rollscan 100-2 can monitor another physical phenomenon, which is the Barkhausen effect. This effect can be defined as a series of abrupt changes or jumps in the magnetization of a steel when the magnetizing field is gradually altered [1]. A set of laboratory experiments were designed to measure the Barkhausen effect as a function of compressive overloading in 300M steel using the Rollscan 100–2. This paper describes the experiments performed and the corresponding results.