As a part of the Earth observing system (EOS) cross- calibration activities before the first flight (denoted AM- 1), a radiometric measurement comparison was held in February 1995 at the NEC Corporation in Yokohama, Japan, Researchers from the National Institute of Standards and Technology (NIST), the National Aeronautics and Space Administration/Goddard Space Flight Center (NASA/GSFC), the University of Arizona Optical Sciences Center, and the National Research Laboratory of Metrology (NRLM) used their portable radiometers to measure the spectral radiance of the advanced spaceborne thermal emission and reflection radiometer (ASTER) visible/near-infrared (VNIR) integrating sphere at three radiance levels. The levels each correspond to 83% of the maximum radiance that is expected to be measured using the three VNIR bands of the EOS ASTER instrument, which are centered at 0.56 micrometer, 0.66 micrometer, and 0.81 micrometer. These bands are referred to as bands 1, 2, and 3. The average of the measurements of the four radiometers was between 1% and approximately 1.5% higher for all three bands when compared to the NEC calibration of the sphere. A comparison of the measurements from the participating radiometers resulted in good agreement. These results are encouraging and will be followed by extension to other EOS AM-1 instrument calibration sources.