This paper presents details from the experience gained over the last twelve years with the fluidized bed method of thermal fatigue testing. The use of the fluidized bed is discussed, and comparisons are made with other methods of testing as to advantages and disadvantages. The design and construction of a fluidized bed test facility is described and performance characteristics noted. Configurations that have been used are disks, wedges, and “window” specimens. All of these specimens may be notched. Temperature gradients in the specimens may be controlled by bed temperatures, time of exposure, and fluidization conditions. The window specimen has been used to examine thermal fatigue resistance of welds between the same and dissimilar materials. The changes that occur during thermal cycling and the effects of thermal stresses on tempering and aging mechanisms are discussed. Finally, selection and treatment of materials to minimize thermal fatigue are considered.