In this investigation the unbalance response and stability of a flexible rotor supported on hydrodynamic journal bearings with rough surfaces have been studied. The influence of the surface roughness patterns on the unbalance response and the stability of a rotor have been evaluated. In this investigation the unbalance response and stability of a flexible rotor supported on hydrodynamic journal bearings with rough surfaces have been studied. The influence of the surface roughness patterns on the unbalance response and the stability of a rotor have been evaluated.