The International Acoustical Imaging Symposium has been held regularly every 18 months for the past 34 years. It is a premier forum for the presentation of advanced research results in both theoretical, experimental development and various applications. The emphasis for the symposium is the exchange of ideas and experience among researchers in different areas of acoustical imaging. The proceedings of the 26th International Acoustical Imaging Symposium, held in Windsor, Ontario, Canada comprise 62 papers including topics of: Biological and Medical, Nondestructive Testing, Acoustic Microscopy, Physics and Mathematics, Components and Systems, Image Processing, Underwater and Geophysical and the History of Acoustical Imaging. Invited talks were given by: Dr. Andrew Briggs, Dr. Robert Green Jr., Dr. Bernhard Tittmann, Dr. Noriyoshi Chubachi, Dr. Joie Jones, Dr. Rainer Michael Schmitt, Dr.Pascal Laugier, Dr. Bryan Huey, Dr. Boro Djordjevic, Dr. Ken Erikson, Dr. Michael Andre, and Dr. Mostafa Fatemi.