During processing hot-rolled steel sheets are exposed to an uneven temperature distribution. Due to the prevailing cooling conditions in the coil a decarburization and an oxidation of the subsurface layer occur, especially along the grain boundaries. The main goals of this diploma thesis were the site-specific preparation of these grain boundaries using Focused Ion Beam preparation techniques and the investigation of the distribution of the alloying elements at these interfaces by means of atom probe tomography. Atom probe tomography enables the determination of the elements around the grain boundaries at atomic resolution in three dimensions. For additional characterization of the grain boundaries complementary techniques, such as transmission electron microscopy and transmission electron backscatter diffraction were used.