This volume constitutes the proceedings of the Thirteenth Inter­ national Symposium on Acoustical Imaging which was held in Minneapolis, Minnesota during October 26-28, 1983. Forty-eight research papers were presented during the meeting by researchers from twelve countries, again demonstrating the true international character of these meetings. Of these presentations this volume contains forty-two complete manuscripts. The abstracts for addi­ tional papers that were not available at publication time are also included. According to the recent tradition of these symposia an inter­ disciplinary program under the general theme of acoustical imaging was organized. This can clearly be observed from the wide range of topics and approaches contained in the following manuscripts. There are papers of mathematical nature dealing with the basis of image formation and algorithms for digitally carrying out specific imaging tasks. One finds manuscripts dealing with the design and construction of imaging transducers as well as complete imaging systems. Applications include medical imaging and nondestructive testing, seismic and underwater imaging. This volume, therefore, should be of interest to active researchers in acoustical imaging as a report on current research and to workers in signal process­ ing, sonics and ultrasonics who are interested in exploring the diverse areas of application for their fields of interest. These proceedings are organized in seven topical sections, paral­ leling the sessions of the conference. These are: Inversion and Tomography, Microscopy, Scattering and Propagation, Tissue and Material Characterization, Signal Processing, Transducers and Arrays, Imaging Systems and Special Techniques.