This book is an outgrowth of several years of teaching and research of the two authors in the field of structural dynamics and control. The content of the book is based on structural dynamics, classical and modern control theory and involves also recent developments that took place with respect to the control of systems with distri­ buted masses. It is hoped that the book will serve the researcher and the practicing engineer in the areas of ci vi 1, mechanical and aeronautical engineering. It may also be of interest to applied mathematicians and to physicists. There is no question that the book can be used as a reference book for advanced courses in the above mentioned areas. The numerous examples will provide students with the necessary material for exercising themselves and for self­ studying. Thanks are due to Mrs. Cynthia Jones for preparing patiently and competently the typescript of the book. The services of Mrs. Linda Strouth, Solid Mechanics Division, University of Waterloo, rendered in producing the camera-ready copy of the book with great skill and devotion, are gratefully acknowledged. Special thanks go to Mr. Ir. Ad. C. Plaizier, at Martinus Nijhoff/Dr. W. Junk, who with much understanding and enthusiasm supervised the production of the book as Publisher. May the readers of it enjoy it, and may they have the fee ling of having gained something in turning to it and using it.