The effectiveness of vibration-based monitoring, (VBM), system may be measured in terms of reduced stoppage rates and increased use of potential bearing life. Analysis of data from roller bearings at two paper mills suggests that greater bearing lives can be safely achieved by increasing the accuracy of the vibration data, This paper relates bearing failures to the observed vibration spectra and their development over the bearings' lives. The literature was found mainly to confirm the author's analysis. A systematic approach which describes the performance and objectives of the studies is discussed. Explanations of the mechanisms behind some frequent modes of early failure and ways to avoid them are suggested. it is shown theoretically, and partly confirmed by the analysis of unfortunately incomplete data from two paper mills over manly years, that accurate prediction of remaining bearing life requires (a) enough vibration measurements, (b) numerate records of operating conditions, (c) better discrimination between frequencies in the spectrum and (d) correlation of (b) and (c). This is because life prediction depends on precise knowledge about primary, harmonic and side band frequency amplitudes and their development over time, Much money could be saved because some policies-utilise as little as half of the bearing's potential life.