In the present paper is investigated the influence of wheel flat on wheel-rail dynamic interaction, considering various parameters of the vehicle, track and wheel defect. The analysis shows that wheel-rail dynamic forces have very large magnitudes, even for low speeds. Over a certain speed, the maximum wheel-rail force is increasing with the vehicle speed. In the lower speed domain, it was noticed a maximum, depending on the flat length, corresponding to the natural frequency of the system. It is found that wheel-rail interaction maximum forces are higher for flats with larger ratio a/L. The maximum dynamic forces are also influenced by the track parameters especially by track stiffness while among the vehicle parameters only the wheelset mass have a perceivable influence.