The 17th International Symposium on Acoustical Imaging was held at Tohoku University, Sendai, Japan, during May 31-June 2, 1988. The symposium was organized by the ultrasonics research group of Tohoku University and the IEEE ijFFC Society, Tokyo Chapter. Of the 128 papers submitted, 88 were presented during the symposium, which comprised 144 researchers from 13 countries. This volume contains 81 papers as the record of the symposium and is clas­ sified into the following sections: (1) Acoustic Microscopy and its Applications; (2) Non-Destructive Evaluation; (3) Signal Processing of Images; (4) Acoustic Measurements and Physical Acoustics; (5) Medical Ultrasonic Diagnostics; (6) Acoustic Sensors; (7) Acoustic Holography and Tomography; (8) Seismic Exploration; and (9) Imaging Instrumentation and Other Techniques. A number of the papers submitted were associated with medical ultrasonic diagnostics and acoustic microscopy, reflecting a major activity in acousti­ cal imaging at Tohoku University. Accordingly, two invited talks were focused on this area: acoustic microscopy by Dr. G. A. D. Briggs of the University of Oxford and medical ultrasonics by Prof. M. Tanaka of Tohoku University. In light of the history of research in this field at our university, we are delighted to have had the opportunity to host the 17th symposium.