This last, the education of pump users, is precisely what this book was intended to do. To what extent we must have achieved our purpose, our readers must decide. My good friend and associate, J. T. (Terry) McGuire, and I have been working very closely together for a long time. Our view of engineering problems and of their solutions coincide to an astonishing degree. When I was asked to prepare a second edition of my book Centrifugal Pumps, it was logical that I turned to Terry and suggested that he be my coauthor on this project. He agreed to do so, and his cooperation has been most valuable, both in improving the resultant work and in easing my burden. It would be presumptuous on my part to pretend that nothing has changed in the technology of centrifugal pumps during the 30 years since I prepared the manuscript for the first edition of this book. Let me, then, speak of some of these changes.