It is now increasingly necessary to predict accurately, at the design stage and without excessive computer costs, the dynamic behaviour of rotating parts of turbomachines, in order to avoid resonant conditions at operating speeds. In this study, the global non-rotating mode shapes of flexible bladed disc-shaft assemblies are used in a modal analysis method for evaluating the dynamic characteristics (frequencies and mode shapes) of the corresponding rotating systems. The non-rotating modes are calculated by using a finite element cyclic symmetry approach. Rotational effects, such as centrifugal stiffening and gyroscopic effects are accounted for, and all the possible couplings between the flexible parts are allowed. An application is presented in order to assess the mathematical model by comparison of the computed results with reference values. (C) 1996 Academic Press Limited