Measurements of stratospheric HNO3 are presented based on new very high resolution (0.002-cm-1 full width at half maximum (FWHM)) solar occultation spectra recorded at 32 ¿N latitude with a balloon-borne interferometer in the region of the HNO3 &ngr;2 band at 5.8 μm and improved spectroscopic line parameters generated for this HNO3 band and the interfering bands of O3 and H2O. The line parameters for HNO3, computed from the spectroscopic constants reported by Maki, are a significant improvement in that the calculated positions are more accurate than previous data and the line list now includes higher J and Ka transitions needed to account for weaker HNO3 absorption features observable in the stratospheric spectra. Verifications of the new line parameters based on the stratospheric spectra and a 0.002-cm-1 resolution HNO3 laboratory spectrum are presented along with comparisons generated with the parameters from the 1986 HITRAN compilation. Significant improvements are apparent for all the updated bands. Finally, the stratospheric HNO3 profile retrieved from the stratospheric solar spectra using a nonlinear least squares fitting algorithm and the new line parameters is reported and compared with previously reported measurements. ¿ American Geophysical Union 1992