An overview is given on the development and trends of refrigerator techniques, and the fundamentals of gas refrigerating machines are outlined. Reminescences on history and development range from the first helium liquefaction (Meissner, 1925) to the comparison of the Leybold helium refrigerator with the Gifford-McMahon refrigerator. PTB-own development and activities comprise the long term operation behaviour of small scale stirling refrigerators, the glas low power cryo-refrigerator, the pressure wave generator, the experimental stirling refrigerator and the refrigerator drive. It is concluded that on account of failures in the long term operation and of the perturbation of electronic systems by moving machine components, the international trend points away from the stirling principle, a possible substitute being the pulse-tube-refrigerator. (WEN)SIGLEAvailable from TIB Hannover: RN 3295(52) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman