Requirements on high efficiency of rotating machinery forces engineers to deal with problems of self-induced vi- brations and balancing of rotors in a serious and scientific manner. The last decade has shown a leap towards the solution of advanced problems of this kind as indicated by the large amount of scientific and engineering papers on rotor dynamics published in international journals. In appreciation of this situation the General Assembly of the International Union of Theoretical and Applied Mecha- nics (IUTAM) at its meeting in Moscow in 1972, acting on a proposal by the Danish Adhering Organization, decided to sponsor an international symposium on the "Dynamics of Rotors" . The scientific planning of the symposium was handed by a scientific committee, consisting of Prof. R.E.D. BISHOP, UK, Prof. S.H. CRANDALL, USA, Prof. F.M. DIMENTBERG, USSR, Dr. A. TONDL, CSSR, Prof. H. ZIEGLER, Switzerland and Prof. F.I. NIORDSON, Denmark, (Chairman). This committee was charged with the selection and invitation of a small number of outstanding scientists in the field, whose contributions to the symposium are presented in this volume. Participation was restricted to invited scientists and there were 87 active participants from 18 countries. Apart from a financial contribution from IUTAM to sup- port travel and subsistence of invited participants, generous contributions were received from the following Danish Companies: Burmeister & Wain, Danfoss, The Danish Sugar- corporation, DISA, Elsinore Shipbuilding Engineer, Kyndby- v~rket, Niro Atomizer, and the Swedish Company STAL-LAVAL. The contributions are gratefully acknowledged.