An international comparison of noise temperature of coaxial (GPC-7) sources at 2 GHz, 4 GHz and 12 GHz has been completed. Participating laboratories included the Physikalisch-Technische Bundesanstalt (PTB); the Bureau National de Metrologie-Laboratoire Central des Industries Electriques (BNM-LCIE); the National Physical Laboratory (NPL); and the National Institute of Standards and Technology (NIST), which served as the pilot laboratory. The comparison was approved by the Working Group on Radiofrequency Quantities (GT-RF) of the Consultative Committee for Electricity and Magnetism (CCEM) as GT-RF 92-2. Full results as well as a brief discussion of measurement procedures and equipment at each laboratory may be found in . Each laboratory measured the noise temperature of two different diode noise sources and reported the noise temperature, the excess noise ratio, and the expanded (k = 2) combined uncertainty for each source at each of the three measurement frequencies. Results are given in Tables 1 and 2. The measurements, which took place between January 1996 and February 1997, were carried out twice at the pilot laboratory: at the beginning of the circulation (NIST-1) and again at the conclusion (NIST-2), in order to confirm that the noise sources had not changed during the comparison. The salient feature of the results is the good agreement among the participating laboratories. For each device, at each frequency, all results are consistent within the expanded (k=2) uncertainties.