Simultaneous retrieval of temperature and water vapor profiles have been obtained by using spectral radiances from the Japanese IMG high resolution interferometer spectrometer. Forward model computations have been performed with the LBLRTM code. The spectral residuals between the IMG measurements and the LBLRTM radiative transfer model are dominated by uncertainty in the IMG spectral instrument function. The impact of these residuals on the retrievals has been significantly mitigated though an approach using reduced resolution. ¿ 2000 American Geophysical Union