This book was written chiefly to help physicists, physical chemists, metallurgists and engineers carry out investigations at low temperatures. It deals with the production and measurement of low temperatures, the handling of liquefied gases on the laboratory scale and the principles and some of the details of the design of experimental temperature control. Physical data used in making low-temperature equipment is given. Enough fundamental principles are included to make this book useful to the advanced university or graduate student. Additional material includes the use of Helium-II cooling to 1K Gifford- McMahon cooling, and other thermometry developments, new physical data on materials and extensive literature references.