In late 1877, Louis Cailletete in France and Raoul Pictet in Switzerland independently succeeded in liquefying oxygen, thereby proving a hypothesis set forth by Antoine Lavoisier nearly 100 years earlier. The theme of the 1977 Cryogenic Engineering Conference "Cryogenics: A Century of Progress-A Chal­ lenge for the Future" properly commemorated this accomplishment by reviewing some of the noteworthy advances since that time and outlining many advances still to come. Both Volumes 23 and 24 of this series provide a good account of the many contributions that were presented at this conference. The 1977 Cryogenic Engineering Conference was appropriately again held in Boulder, Colorado where the first Cryogenic Engineering Conference was initiated 23 years ago by the late Russell B. Scott, then Chief of the Cryogenic Engineering Laboratory of the National Bureau of Standards. The Cryogenic Engineering Conference Board is extremely grateful to members of the National Bureau of Standards and the University of Colorado for serving as hosts for this meeting of cryogenic specialists from all over the world. The Cryogenic Engineering Conference is again pleased to have had the International Cryogenic Materials Conference co-host this biennial meeting for the second time in succession. This joint effort again has permitted an in-depth coverage of research on technical materials in areas currently receiving primary attention by the cryogenic engineering community. The Proceedings of the Inter­ national Cryogenic Materials Conference will be published as Volume 24 of the Advances in Cryogenic Engineering.