This book is another updating revision of the theory of vibration with applications in keeping with the continuing advances in modern technology and pedagogy additional changes have been made in the subject matter arrangement of topics mode of presentation and emphasis. In the first four chapters which deal with single degree of freedom systems the simple physical approach of the previous edition has been adhered to and hopefully improved upon. In chapter 2 the rayleigh energy method for conservative systems is supplemented by the virtual work method. Frequency response concepts using complex algebra have been added to the third chapter. The section on computer calculation still maintains its place of importance.