One of the critical components of many cryogenic systems, such as liquefiers and cryocoolers, is the heat exchanger. In many conventional systems, such as regenerative gas turbine power plants, the system will operate even if the heat exchanger is not highly effective (e.g., less than 5%). In contrast, a cryogenic liquefier will produce no liquid if the heat exchanger effectiveness is less than approximately 85% (Barron 1985). In this chapter, some of the design principles for several types of heat exchangers that are commonly used for cryogenic service will be examined. These heat exchangers include the Giauque–Hampson exchanger, the plate-fin exchanger, and the perforated plate exchanger. Secondary effects, including longitudinal conduction and variable specific heat, will also be considered because they may become of primary importance in high-performance cryogenic heat exchangers. The storage-type heat exchanger or regenerator is extensively used in cryogenic systems because of some of its beneficial characteristics, which are listed in Section 10.10. The design of regenerators will also be covered.