This volume presents the proceedings of the Third International Symposium on Acoustical Holography, which was held at the Newporter Inn, Newport Beach, on 29-31 July 1970. The symposium was sponsored by the Douglas Advanced Research Laboratories, McDonnell Douglas Corporation, and the Acoustical Society of America. Twenty papers were presented and these each appear as a chapter in this volume. The chapters are grouped into five sections. The sections are I Medical and Biolog­ ical, II Bragg Imaging, III Nondestructive Testing, IV Underwater and Long Wavelength, and V Theory and Methods. The reader is cautioned only to use the sec­ tional titles as a rough guide. For instance, the reader interested in new methods should not just read section V since he will find a new liquid surface relief method de­ scribed in chapter lOin section III. In an effort to reduce the time delay between the meeting and the publication date, the publishers have pro­ duced this volume using the shoot-from-manuscript method instead of the mote time consuming typesetting method that was used on the previous volumes. As a result there may be differences in notation and definitions used for one chapter to another. However this should not cause con­ fusion since all symbols and definitions are stated in each chapter. The editor wishes to thank the session chairmen, Dr. Vincent Salmon, Stanford Research Institute; Dr. Isadore Rudnick, University of California at Los Angeles; Dr. Lewis Larmore, McDonnell Douglas Corporation; Dr.