This symposium on 'Engineering with Nuclear Explosives' reports to the Plowshare community, both national and international, the progress achieved since April 1964, the date of the Third Plowshare Symposium. In structuring the technical presentations, contributions of broadest interest were placed at the beginning, thus forming a common base of current information and applied science understanding developed in support of Plowshare technology. Sessions of speciality or pertaining to specific areas of application and engineering follow logically in the program. The Plenary Session reviewed the current status of the Plowshare Program from the technical, government, and industrial points of view. The 112 papers presented at 15 technical sessions covered all technical aspects of the Plowshare Program. The conference summary reviewed principal themes, areas of significant advance, and subjects requiring further attention that emerged during the technical conference. These proceedings are the record of the symposium.