The rail/wheel contact comprises interactions of thermal and mechanical loadings which lead to microstructural changes in the wheel. These were investigated on a wheel from a regional train using metallographic examinations, X-ray diffraction for phase and residual stress analyses. The results show that the microstructural alterations, the carbon content and the residual stress distribution depend on the loading profile of the wheel. The formation of two different martensites (tetragonal and cubic martensite) on a wheel surface could be detected at different positions. The martensites are characterized by high hardness values, increased carbon contents in the lattice and an increased level of compressive residual stresses. Detailed structural analyses of the martensites which were formed under locally different loading and time conditions gave evidence for different structural evolutions.