The use of magnetic Barkhausen Noise Analysis (BNA) has been proven to be an effective tool for the non-destructive detection of microstructural anomalies in ferrous materials. Used as an in-process tool for the detection of grinding burn, heat treat defects and stresses, BNA is a quick comparative and quantitative alternative to traditional destructive methods. Applications of BNA as a quality control tool in gear production have existed for nearly two decades. This paper presents examples that demonstrate how BNA is used to evaluate changes in microstructural properties. Quantitative results correlate BNA test values to X-Ray diffraction values for the detection of changes in surface residual stress. Other quantitative analysis correlates BNA test values to surface hardness values for the detection of re-tempering burn. Qualitative results correlate BNA test values to acid etch patterns/colors for the detection of grinding burn defects. Robotically automated systems can test gear teeth and provide immediate feedback for process control and quality assurance.