Cryocoolers 12 The last two years have witnessed a continuation in the breakthrough shift toward pulse tube cryocoolers for long life high reliability cryocooler applications. One class of pulse tubes that has reached maturity is referred to as “Stirling type” because they are based on the linear Oxford Stirling cooler type compressor; these generally provide cooling in the 30 to 100 K temperature range and operate at frequencies from 30 to 60 Hz. The other type of pulse tube cooler making great advances is the so called “Gifford McMahon type. ” Pulse tube coolers of this type use a G M type compressor and lower frequency operation to achieve temperatures in the 2 to 10 K temperature range. Nearly a third of this proceedings covers these new developments in the pulse tube arena. Complementing the work on low temperature pulse tubes is substantial continued progress on rare earth regenerator materials and Gifford McMahon coolers. These technologies continue to make great progress in opening up the 2 4 K market. Also in the commercial sector continued interest is being shown in the development of long life low cost cryocoolers for the emerging high temperature superconductor electronics market particularly the cellular telephone base station market. At higher temperature levels closed cycle J T or throttle cycle refrigerators are taking advantage of mixed refrigerant gases to achieve low cost cryocooler systems in the 65 to 80 K temperature range. Government Cryocooler Development Programs Space Stirling Cryocooler Developments Tactical and Commercial Stirling Cryocoolers Tactical and Commercial Pulse Tube Cryocoolers Space Pulse Tube Cryocooler Developments Linear Compressor Development and Modeling GM Type Pulse Tube Coolers for Low Temperatures Hybrid Cryocoolers Using Pulse Tubes Pulse Tube Analyses and Experimental Measurements GM Refrigerator Developments Thermoacoustic Refrigerator Investigations Regenerator Materials Development Regenerator Performance Analyses and Tests Turbo Brayton Cryocooler Developments J T and Throttle Cycle Cryocooler Developments Sorption Cryocooler Developments Sub Kelvin and Optical Refrigerator Developments Cryocooler Integration Technologies Space Cryocooler Applications Commercial Cryocooler Applications.