Plain carbon steel cylinders were heat treated and quenched in order to study the effects of heat treating on residual stresses and microstructure. Residual stress measurements were obtained via X-ray diffraction using the sin 2 Ψ method and microstructure was characterized based on the associated peak widths. Measurements were made both at the surface and through depth following electropolishing. Triaxial stress gradients were observed in all test samples with concomitant varying microstructural characteristics. The method used to measure residual stresses in this study is typical and recommended for general practice.