This article is devoted to diagnostics of rotating machines – electric motors and generators. It describes their basic characteristics and failure modes in terms of statistics and experience. The methods of multi-parametric approach to electrical machines diagnostics are listed. The analysis methods based of vibration measurement are emphasized due to the fact that vibration analysis is the best way to define the condition of any rotational machines. In addition, vibration can be, in some circumstances, successfully used for the evaluation of electromagnetic faults as well. The article introduces actual examples of deficiencies of mechanical and electrical motors using different diagnostics methods.