Measurements were done to determine the influence of a transverse crack on the mobility of a rotor-bearing system. The results show that the mobility changes substantially due to the presence of crack and follows definite trends with the crack depth and direction of force application. The significant changes in mobility were observed at the natural frequency and at the running frequency of the rotor system. Good agreement between the experimental results and numerical simulations has been observed. The measurement of mobility has been suggested for crack detection and condition monitoring of rotor-bearing systems. © 2002 Acoustical Society of America.