For steel samples made of S690QL the influence of residual stresses on microhardness is systematically investigated using a combined application of universal hardness measurements and residual stress analysis by X-ray diffraction. Measurements were carried out on a path along the bending height on the side face of a bending bar exposed to 4-point-bending (Fig. 1). Elasto-plastic bending causes an inhomogeneous deformation of the steel specimen and hence results in a characteristic macro- and microresidual stress distribution. By the use of a 4-point-bending device, which can be mounted both on the hardness testing machine as well as on the X-ray diffractometer, in-situ measurements up to an elasto-plastic loading of the material enabled to distinguish between the effects of loading stresses, residual stresses and strain hardening on hardness. Loading as well as residual stresses have a marked influence on the results of microhardness measurements. This effect overlaps with consequences of strain hardening and influences characteristic hardness distributions as a function of-the bending height of the bar.