Vertically downwelling radiance spectra under clear sky were calculated in the 500 to 3000 wavenumber region. The calculations were carried out at wavenumber intervals varying between 20 and 80 cm-1. The discrete ordinate radiative transfer code was used, along with the exponential sum fitting of transmission of water vapor, ozone, carbon dioxide, carbon monoxide, methane, and nitrous oxide. The spectral data base for the exponential sum fitting was obtained from the LOWTRAN7 transmittances. Observed vertical profiles of temperature, water vapor and ozone, obtained with conventional radiosondes and with Raman lidar, were used as inputs to the calculations. The sounding data were obtained during the Spectral Radiance Experiment (SPECTRE), held as part of FIRE Cirrus II in Coffeyville, Kansas, USA in November - December 1991. The calculated radiance spectra are compared to those calculated from LOWTRAN7. One spectrum is also compared to radiances observed near simultaneously during SPECTRE by the University of Wisconsin Atmospheric Emitted Radiance Interferometer instrument. The comparisons show a bias of 0.1 - 0.25 mW m-2 sr-1 (cm-1)-1 when averaged over the range of 560 to 3,000 cm-1. This study was conducted in part in the framework of the Intercomparison of Radiation Codes in Climate Models.