The University of Colorado and the National Bureau of Standards have once again served as hosts for the Cryogenic Engineering Conference in Boulder, Colorado. In presenting the papers of this twelfth annual meeting, the 1966 Cryogenic Engineering Conference Committee has again recognized the excellent cooperation which has existed between these two organizations over the past decade with regard to both cryogenic research and conference activity. This cooperation was demonstrated not only at the 1966 Cryogenic Engineering Conference but also at the International Institute of Refrigeration, Commission I Meeting, which was also hosted by these two organizations immediately following the Cryogenic Engineering Conference. These two meetings have provided attendees with one of the most comprehensive coverages of cryogenic topics that has ever been presented at one location. Emphasis on major international advances in helium technology at the International Institute of Refrigeration, Commission I Meeting has been possible largely through the National Science Foundation Grant GK 1116 to the University of Colorado. The Cryogenic Engineering Conference Committee gratefully acknowledges this support because of its valuable international contribution to the Cryogenic Engineering Conference. As in the past, the Cryogenic Engineering Conference Committee is grateful for the continued assistance of all the dedicated workers in the cryogenic field who have contributed their time reviewing the preliminary papers for the program and the final manuscripts for this volume.