This course is tailored to those who have a general knowledge of cryocoolers and wish to delve deeper into the operating principles of regenerative cycles represented by Stirling, Gifford-McMahon, and pulse tube cryocoolers. The course begins with the thermodynamic and heat transfer fundamentals necessary for understanding the theory behind regenerative cryocooler operation. Various losses and energy flows, such as enthalpy, entropy, acoustic power, Gibbs free energy, and exergy, in regenerative cryocoolers are discussed in both ideal gas and real gas operating fluids. Phasor analysis is introduced to show how it can provide a simple visual model for the relationship between flow and pressure in various components, such as compressors, displacers, regenerators, heat exchangers, pulse tubes, and inertance tubes. Available numerical modeling software including DeltaE, REGEN3.3, and Sage are explained and discussed in the course. Approaches to the design and optimization of regenerative cryocoolers for various conditions are presented in the final part of the course.