The article observes problems of detection of rolling bearing damages in rail vehicles. Two methods of bearing damage detection are examined – according to heating of axleboxes and by vibro-diagnostic manner. The disadvantage of vibro-diagnostic method is that a contact vibration sensor is used for vibration diagnostics, intervention into rail vehicle structure is required. The method according to heating of axle-boxes also has drawbacks. The same temperature value of axle-box in various conditions may characterize different bearing technical state. The Authors studied a possibility to use temperature change intensity parameters as the diagnostics criteria. Based on the examples of axle-box temperature measurement data, Authors developed and proposed a methodology for detecting axle-box bearings defects. The Authors suggest the use the method according to heating of axle-boxes. The given example proofs that the fact of the presence of their damages can be unambiguously identified by the intensity of temperature change of the axle-boxes.