It is altogether fitting that the American Vacuum Society commemorate its 40th anniversary by paying tribute to the pioneers who laid the foundations of modern vacuum science. Through new biographies and historical reviews, and reprints of seminal papers, Vacuum Science and Technology: Pioneers of the 20th Century gives us a fresh appreciation for the groundbreaking work done in the first part of this century. This volume begins with a brief history of the AVS by former Westinghouse researcher Jack Singleton. Section 1 presents original biographies of those scientists and engineers who were at the vanguard of vacuum technology and whose contributions greatly furthered our knowledge of the production, measurement, and use of vacuum. These include such important figures as Pieter Clausing, Wolfgang Gaede, Irving Langmuir, and Martin Knudsen. Section 2 covers some of the major breakthroughs of the half-century from 1900 to 1960, including reviews of the development of diffusion pumps, molecular-drag pumps, high-vacuum turbopumps, and the quest for ultrahigh vacuum. Finally, Section 3 affords us an opportunity to revisit papers that are now regarded as milestones in vacuum science. Among them are Saul Dushman's 1915 paper, "Theory and Use of the Molecular Gauge", Pieter Clausing's 1932 classic, "The Flow of Highly Rarefied Gases through Tubes of Arbitrary Length", and L.D. Hall's 1958 piece, "Electronic Ultra-High Vacuum Pump". In putting together this work, editor Paul A. Redhead called upon some of the most highly respected names in the field today, including Daniel Alpert, H. Adam, W. Steckelmacher, P.S. Choumoff, Gunter Reich, J.M. Lafferty, and George Wise. For researchers andtechnicians involved in vacuum technology and related fields, and for those interested in the rich history of the field, this anniversary volume will prove both entertaining and informative.